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SYSTEM 

;0  F 


ANATOMY. 


A 


COMPENDIOUS  SYSTEM 


O F 

ANATOMY. 

IN  SIX  PARTS. 


I.  OSTEOLOGY. 

IX.  OF  THE  MUSCLES.  &g. 
HL  OF  THE  ABDOMEN. 


IV.  OF  THE  THORAX. 

V.  OF  THE  BRAIN  AND  NERVES. 

VI.  OF  THE  SENSES. 


FROM  THE  ENCYCLOPEDIA. 


Illustrated,  "with  Twelve  large  Copperplates. 


PHILADELPHIA : 

PRINTED  BY  ARCHIBALD  BARTRAM, 

FOR  THOMAS  DOBSON,  AT  THE  STONE  HOUSE,  No.  4fc 
SOUTH  SECOND.STREET. 


1805, 


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afj  rui-.  : n.i  - - . <;  ■ 


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• * 

CONTENTS. 


Page. 

Introduction  9 

1.  History  of  anatomy  ibid. 

2.  View  of  the  subject  in  general , and 

plan  of  the  following  treatise  40 

Part  I.  Osteology  57 

Sect.  I.  Of  the  bones  in  general , with  their 

appendages , &c.  5 8 

II.  Of  the  bones  of  the  head  71 

1.  Bones  of  the  cranium  and  face  72 

2.  Proper  bones  of  the  face  85 

3.  Of  the  teeth  91 

4.  os  hyoides  98 

III.  bones  of  the  trunk  99 

1.  spine  ibid. 

2.  bones  of  the  thorax  108 

3.  bones  of  the  pelvis  ill 

IV.  Extremities  114 

1.  upper  extremities  115 

1.  shoulder  ibid. 

2.  bones  of  the  arm  117 

3.  bones  of  the  hand  121 

2.  lower  extremities  124 

1.  thigh  ibid. 

2.  rotula , or  knee-pan  126 

3.  leg  127 


( Vi  ) 


Page 


4. 

Of  the  foot 

129 

4. 

ossa  sesamoidea 

133 

Explanation  of  the  plates  of  osteology 

134,  152 

Part  II.  Of  the  Soft  Parts  in  general  157 

Of  the 

common  integuments , with  their 

appendages  ; and  of  the  muscles 

ibid. 

Sec.  I. 

Of  the  skin 

159 

1. 

scarf-skin 

ibid. 

2. 

rete  mucosum 

160 

3. 

cutis , or  true  skin 

161 

4. 

glands  of  the  skin 

162 

5. 

insensible  perspiration  and 

sweat 

163 

6. 

nails 

166 

7 . 

hair 

167 

8. 

cellular  membrane  and  fat  168 

II. 

muscles 

170 

particular  muscles 

180 

A table  of  the  muscles  arranged  according 
to  their  situation  181 


Explanation  of  plates  XXIII.  XXIV.  230,235 

Part  III.  Of  the  Abdomen,  or  Low- 
er Belly.  236 

Sec.  I.  Of  the  peritoneum  238 

II.  omentum  239 


( vii  ) 


Page 

Sec.  III.  Of  the  stomach  241 

IV . oesophagus  243 

h . intestines  244 

VI.  mesentery  248 

VII.  pancreas  251 

VIII.  liver  253 

IX.  gall-bladder  255 

X.  spleen  258 

XI.  glandulre  renales , kidneys 

and  ureters  259 

XII.  urinary  bladder  262 

XIII.  Of  digestion  266 

XIV.  Of  the  course  of  the  chyle  and  of 

the  lymphatic  system  278 

XV.  Of  the  generative  organs ; of 

conception , &c.  284 

1.  The  male  organs  ibid. 

2.  Female  organs  of  generation  296 

3.  Of  conception 

4.  Of  the  foetus  in  utero  304 


4.  Of  the  foetus  in  utero 
Explanation  of  plates  XXV.  XXVI. 


and  XXVII. 

309,  316 

Part  IV.  Of  the  Thorax 

318 

Sec.  I.  Of  the  breasts 

319 

II 

pleura 

320 

III. 

thymus 

322 

IV. 

diaphragm 

ibid. 

V. 

trachea 

324 

* ( viii  ) 

Page 

■Sec.  VI.  Of  the  lungs  327 

VII.  Of  respiration  ' 329 

VIII.  Of  the  voice  334 

IX.  Of  dejection  336 

X.  Of  the  pericardium , and  of  the 

heart , and  its  auricles  337 

XI.  Angiology , or  a description  of 

the  blood-vessels  342 

XII.  Of  the  action  of  the  heart , 

auricles , and  arteries  352 

XIII.  Of  the  circulation  354 

X/Fi  nature  of  the  blood  355 

XF.  Of  nutrition  3 57 

XFX  Of  the  glands  and  secretions  3 59 

Explanation  of  plate  XXVIII.  364 

Part  V.  Of  the  Brain  and  Nerves  366 

Sec.  I.  Of  the  brain  and  its  integuments  ibid. 

II.  nerves  379 

Explanation  of  plate  XXIX.  386 

Part  VI.  Of  the  Senses  and  their 

Organs  390 

Sec.  I.  Of  touch  ibid. 

II.  taste  391 

III.  smelling  39S 

IV.  hearing  396 

V.  vision  404 

Explanation  of  plate  XXX.  415 


SYSTEM 


OF 

ANATOMY. 


ANATOMY, 


THE  art  of  dissecting,  or  artificially  separat- 
ing and  taking  to  pieces,  the  different 
parts  of  the  human  body,  in  order  to  an  exact 
discoveiy  of  their  situation,  structure,  and  (eco- 
nomy.— The  word  is  Greek,  avaro/ni)  ; derived  from 
to  dissect,  or  separate  by  cutting. 

INTRODUCTION. 

1.  History  of  Anatomy. 

This  art  seems  to  have  been  very  ancient ; 
though,  for  a long  time,  known  only  in  an  im- 
perfect manner. — The  first  men  who  lived 
must  have  soon  acquired  some  notions  of  the 
structure  of  their  own  bodies,  particularly  of 
the  external  parts,  and  of  some  even  of  the 
internal,  such  as  bones,  joints,  and  sinews, 
which  are  exposed  to  the  examination  of  the 
senses  in  living  bodies. 

B 


10 


History  of  Anatomy . 


This  rude  knowledge  must  have  been  gra- 
dually improved,  by  the  accidents  to  which 
the  body  is  exposed,  by  the  necessities  of  life, 
and  by  the  various  customs,  ceremonies,  and 
superstitions,  of  different  nations.  Thus,  the 
observance  of  bodies  killed  by  violence,  at- 
tention to  wounded  men,  and  to  many  diseases, 
the  various  ways  of  putting  criminals  to  death, 
the  funeral  ceremonies,  and  a variety  of  such 
things,  must  have  shown  men  every  day  more 
and  more  of  themselves  ; especially  as  curio- 
sity and  self-love  would  here  urge  them  pow- 
erfully to  observation  and  reflection. 

The  brute-creation  having  such  an  affinity 
to  man  in  outward  form,  motions,  senses,  and 
ways  of  life  ; the  generation  of  the  species, 
and  the  effect  of  death  upon  the  body,  be- 
ing observed  to  be  so  nearly  the  same  in  both  ; 
the  conclusion  was  not  only  obvious,  but  un- 
avoidable, that  their  bodies  were  formed  near- 
ly upon  the  same  model.  And  the  opportu- 
nities of  examining  the  bodies  of  brutes  were 
so  easily  procured,  indeed  so  necessarily  oc- 
curred m the  common  business  of  life,  that 
the  huntsman  in  making  use  of  his  prey,  the 
priest  in  sacrificing,  the  augur  in  divination, 
and,  above  all,  the  butcher,  or  those  who  might 
out  of  curiosity  attend  upon  his  operations, 
must  have  been  daily  adding  to  the  little  stock 
of  anatomical  knowledge.  Accordingly  we 
find,  in  fact,  that  the  South-sea  islanders,  who 
have  been  left  to  their  own  observation  and 
'reasoning,  without  the  assistance  of  letters, 
have  yet  a considerable  share  of  rude  or  wild 


History  of  Anatomy.  ii 

anatomical  and  physiological  knowledge.  Dr. 
Hunter  informs  us,  that  when  Omai  was  in 
his  museum  with  Mr.  Banks,  though  he  could 
not  explain  himself  intelligibly,  they  plainly 
saw  that  he  knew  the  principal  parts  of  the  bo- 
dy, and  something  likewise  of  their  uses  ; and 
manifested  a great  curiosity  or  desire  of  hav- 
ing the  functions  of  the  internal  parts  of  the 
body  explained  to  him,  particularly  the  relative 
functions  of  the  two  sexes,  which  with  him 
seemed  to  be  the  most  interesting  object  of 
the  human  mind. 

We  may  further  imagine,  that  the  philoso- 
phers of  the  most  early  ages,  that  is,  the  men 
of  curiosity,  observation,  experience  and  re- 
flection, could  not  overlook  an  instance  of  na- 
tural organization,  which  was  so  interesting, 
and  at  the  same  time  so  wonderful,  more  es- 
pecially such  of  them  as  applied  to  the  study 
and  cure  of  diseases.  We  know  that  physic 
was  a branch  of  philosophy  till  the  age  of 
Hippocrates. 

Thus  the  art  must  have  been  circumstanced 
in  its  beginning.  We  shall  next  see  from  the 
testimony  of  historians  and  other  writers, 
how  it  actually  appeared  as  an  art,  from  the 
time  that  writing  was  introduced  among  men  5 
how  it  was  improved  and  conveyed  down  to  us 
through  a long  series  of  ages. 

Civilization  and  improvements  of  every  kind, 
would  naturally  begin  in  fertile  countries  and 
healthful  climates,  where  there  would  be  lei- 
sure for  reflection,  and  an  appetite  for  amuse- 
ment. Accordingly,  writing,  and  many  other 


12 


History  of  Anatomy. 


useful  and  ornamental  inventions  and  arts,  ap- 
pear to  have  been  cultivated  in  the  eastern  parts 
of  Asia  long  before  the  earliest  times  that  are 
treated  of  by  the  Greek  or  other  European  wri- 
ters ; and  that  the  arts  and  learning  of  those 
eastern  people  were  in  subsequent  times  gra- 
dually communicated  to  adjacent  countries,  es- 
pecially by  the  medium  of  traffic.  The  cus- 
toms, superstitions,  and  climate  of  eastern  coun- 
tries, however,  appear  to  have  been  as  unfa- 
vourable to  practical  anatomy,  as  they  were 
inviting  to  the  study  of  astronomy,  geometry, 
poetry,  and  all  the  softer  arts  of  peace. 

Animal  bodies  there,  run  so  quickly  into 
nauseous  putrefaction,  that  the  early  inha- 
bitants must  have  avoided  such  offensive  em- 
ployments, as  anatomical  inquiries,  like  their 
posterity  at  this  day.  And,  in  fact,  it  does 
not  appear,  by  the  writings  of  the  Greci- 
ans, or  Jews,  or  Phoenicians,  or  of  other  eas- 
tern countries,  that  anatomy  was  particularly 
cultivated  by  any  of  those  eastern  nations.  In 
tracing  it  backwards  to  its  infancy,  we  cannot 
go  farther  into  antiquity  than  the  times  of  the 
Grecian  philosophers.  As  an  art  in  the  state 
of  some  cultivation,  it  may  be  said  to  have 
been  brought  forth  and  bred  up  among  them 
as  a branch  of  natural  knowledge. 

The  sera  of  philosophy,  as  it  was  called, 
began  with  Thales  the  Mdesian  being  declar- 
ed by  a very  general  consent  of  the  people, 
the  most  wise  of  all  the  Grecians,  480  years  be- 
fore Christ.  The  philosophers  of  his  school, 
which  was  called  the  Ionian,  cultivated  prin- 


History  of  Anatomy. 


13 


cipally  natural  knowledge.  Socrates,  the  se- 
venth in  succession  of  their  great  teachers,  in- 
troduced the  study  of  morals,  and  was  thence 
said  to  bring  down  philosophy  from  heaven, 
to  make  men  truly  wise  and  happy. 

In  the  writings  of  his  scholar  and  successor 
Plato,  we  see  that  the  philosophers  had  care- 
fully considered  the  human  body,  both  in  its 
organization  and  functions  ; and  though  they 
had  not  arrived  at  the  knowledge  of  the  more 
minute  and  intricate  parts,  which  required 
the  successive  labour  and  attention  of  many 
ages,  they  had  made  up  very  noble  and  com- 
prehensive ideas  of  the  subject  in  general. 
The  anatomical  descriptions  of  Xenophon  and 
Plato  have  had  the  honour  of  being  quoted 
by  Longinus  (§xxxii.)  as  specimens  of  sub- 
lime writing ; and  the  extract  from  Plato  is 
still  more  remarkable  for  its  containing  the 
rudiments  of  the  circulation  of  the  blood.  “The 
heart  (says  Plato)  is  the  centre  or  knot  of  the 
blood-vessels  ; the  spring  or  fountain  of  the 
blood  which  is  carried  impetuously  round ; the 
blood  is  the  pabulum  or  food  of  the  flesh ; 
and,  for  the  purpose  of  nourishment,  the  body 
is  laid  out  into  canals,  like  those  which  are 
drawn  through  gardens,  that  the  blood  may 
be  conveyed,  as  from  a fountain,  to  every 
part  of  the  pervious  body.” 

Hippocrates  was  nearly  contemporary  with 
the  great  philosophers  of  whom  we  have  been 
speaking,  about  400  years  before  the  Christi- 
an sera.  He  is  said  to  have  separated  the  pro- 
fession of  philosophy  and  physic,  and  to  have 


14 


History  of  Anatomy. 


been  the  first  who  applied  to  physic  alone  as 
the  business  of  his  life.  He  is  likewise  gene- 
rally supposed  to  be  the  first  who  wrote  upon 
anatomy.  We  know  of  nothing  that  was  writ- 
ten expressly  upon  the  subject  before ; and 
the  first  anatomical  dissection  which  has  been 
recorded,  was  made  by  his  friend  Democritus 
of  Abdera. 

If,  however,  we  read  the  works  of  Hippo- 
crates with  impartiality,  and  apply  his  ac- 
counts of  the  parts  to  what  we  now  know  of 
the  human  body,  we  must  allow  his  descrip- 
tions to  be  imperfect,  incorrect,  sometimes  ex- 
travagant, and  often  unintelligible,  that  of  the 
bones  only  excepted.  He  seems  to  have  stu- 
died these  with  more  success  than  the  other 
parts,  and  tells  us  that  he  had  an  opportunity 
of  seeing  an  human  skeleton. 

From  Hippocrates  to  Galen,  who  flourish- 
ed towards  the  end  of  the  second  century,  in 
the  decline  of  the  Roman  empire,  that  is,  in 
the  space  of  600  years,  anatomy  was  greatly 
improved ; the  philosophers  still  considering 
it  as  a most  curious  and  interesting  branch  of 
natural  knowledge,  and  the  physicians,  as  a 
principal  foundation  of  their  art.  Both  of 
them,  in  that  interval  of  time,  contributed  dai- 
ly to  the  common  stock,  by  more  accurate  and 
extended  observations,  and  by  the  lights  of 
improving  philosophy. 

As  these  two  great  men  had  applied  very 
particularly  to  the  study  of  animal  bodies, 
they  not  only  made  great  improvements,  es- 
pecially in  physiology,  but  raised  the  credit 


History  of  Anatomy. 


15 


of  natural  knowledge,  and  spread  it  as  wide 
as  Alexander’s  empire. 

Few  of  Aristotle’s  writings  were  made  pub- 
lic in  his  lifetime.  He  affected  to  say  that 
they  would  be  unintelligible  to  those  who 
had  not  heard  them  explained  at  his  lectures  : 
and,  except  the  use  which  Theophrastus  made 
of  them,  they  were  lost  to  the  public  for  above 
130  years  after  the  death  of  Theophrastus; 
and  at  last  came  out  defective  from  bad  pre- 
servation, and  corrupted  by  men,  who,  with- 
out proper  qualifications,  presumed  to  correct 
and  supply  what  was  lost. 

From  the  time  of  Theophrastus,  the  study 
of  natural  knowledge  at  Athens  was  for  ever 
on  the  decline  ; and  the  reputation  of  the  Ly- 
ceum and  Academy  was  almost  confined  to 
the  studies  which  are  subservient  to  orato- 
ry and  public  speaking. 

The  other  great  institution  for  Grecian  edu- 
cation, was  at  Alexandria  in  Egypt.  The  first 
Ptolemies,  both  from  their  love  of  literature, 
and  to  give  true  and  permanent  dignity  to  their 
empire,  and  to  Alexander’s  favourite  city,  set 
up  a grand  school  in  the  palace  itself,  with 
a museum  and  library,  which,  we  may  say, 
has  been  the  most  famed  in  the  world.  An- 
atomy, among  other  sciences,  was  publicly 
taught ; and  the  two  distinguished  anatomists 
were  Erasistratus  the  pupil  and  friend  of  The- 
ophrastus, and  Herophilus.  Their  volumi- 
nous works  are  all  lost ; but  they  are  quoted 
by  Galen  almost  in  every  page.  These  pro- 
fessors were  probably  the  first  who  were  au- 


16 


History  of  Anatomy. 


thorised  to  dissect  human  bodies  ; a peculiari- 
ty which  marks  strongly  the  philosophical 
magnanimity  of  the  first  Ptolemy,  and  fixes 
a great  sera  in  the  history  of  anatomy.  And  it 
was,  no  doubt,  from  this  particular  advantage 
which  the  Alexandrians  had  above  all  others, 
that  their  school  not  only  gained,  but  for  ma- 
ny centuries  preserved,  the  first  reputation 
for  medical  education.  Ammianus  Marcelli- 
nus,  who  lived  about  6 50  years  after  the 
schools  were  set  up,  says,  they  were  so  fa- 
mous in  his  time,  that  it  was  enough  to  se- 
cure credit  to  any  physician,  if  he  could  say 
he  had  studied  at  Alexandria. 

Herophilus  has  been  said  to  have  anato- 
mized 700  bodies.  We  must  allow  for  exagge- 
ration. Nay,  it  was  said,  that  both  he  and 
Erasistratus  made  it  a common  practice  to 
open  living  bodies,  that  they  might  discover 
the  more  secret  springs  of  life.  But  this,  no 
doubt  was  only  a vulgar  opinion,  rising  from 
the  prejudices  of  mankind ; and  accordingly, 
without  any  good  reason,  such  tales  have 
been  told  of  modern  anatomists,  and  have  been 
believed  by  the  vulgar. 

Among  the  Romans,  though  it  is  pro- 
bable they  had  physicians  and  surgeons  from 
the  foundation  of  the  city,  yet  we  have  no 
account  of  any  of  these  applying  themselves 
to  anatomy  for  a very  long  time.  Archagathus 
was  the  first  Greek  physician  established  in 
Rome,  and  he  was  banished  the  city  on  ac- 
count of  the  severity  of  his  operations. — 
Asclepiades,  who  flourished  in  Rome  101 


History  of  Anatomy. 


17 


years  after  Archagathus,  in  the  time  of  Pom- 
pey,  attained  such  a high  reputation  as  to  be 
ranked  in  the  same  class  with  Hippocrates. 
He  seemed  to  have  some  notion  of  the  air  in 
respiration  acting  by  its  weight ; and  in  ac- 
counting for  digestion,  he  supposed  the  food 
to  be  no  farther  changed  than  by  a comminu- 
tion into  extremely  small  parts,  which  being 
distributed  to  the  several  parts  of  the  body, 
is  assimilated  to  the  nature  of  each.  One 
Cassius,  commonly  thought  to  be  a disciple 
of  Asclepiades,  accounted  for  the  right  side 
of  the  body  becoming  paralytic  on  hurting  the 
left  side  of  the  brain,  in  the  same  manner  as 
has  been  done  by  the  moderns,  viz.  by  the 
crossing  of  the  nerves  from  the  right  to  the  left 
side  of  the  brain. 

From  the  time  of  Asclepiades  to  the  second 
century,  physicians  seem  to  have  been  great- 
ly encouraged  at  Rome  ; and,  in  the  writings  of 
Celsus,  Rufus,  Pliny,  Ccelius,  Aurelianus, 
and  Arseteus,  we  hnd  several  anatomical  ob- 
servations, but  mostly  very  superficial  and 
inaccurate.  Towards  the  end  of  the  second 
century  lived  Claudius  Gallenus  Pergarnus, 
whose  name  is  so  well  known  in  the  medical 
world.  He  applied  himself  particularly  to  the 
study  of  anatomy,  and  did  more  in  that  way 
than  all  that  went  before  him.  Pie  seems, 
however,  to  have  been  at  a great  loss  for  hu- 
man subjects  to  operate  upon ; and  therefore 
his  descriptions  of  the  parts  are  mostly  taken 
from  brute  animals.  His  works  contain  the 
fullest  history  of  anatomists,  and  the  most 

C 


18 


History  of  Anatomy. 


complete  system  of  the  science,  to  be  met 
with  any  where  before  him,  or  for  several 
centuries  after;  so  that  a number  of  passages 
in  them  were  reckoned  absolutely  unintelligible 
for  many  ages,  until  explained  by  the  disco- 
veries of  succeeding  anatomists. 

About  the  end  of  the  fourth  century,  Ni- 
mesius  bishop  of  Emissa  wrote  a treatise  on 
the  nature  of  man,  in  which  it  is  said  were 
contained  two  celebrated  modern  discoveries  ; 
the  one,  the  uses  of  the  bile,  boasted  of  by 
Sylvius  de  la  Boe  ; and  the  other,  the  circula- 
tion of  the  blood.  This  last,  however,  is 
proved  by  Dr.  Friend,  in  his  history  of  phy- 
sic, p.  229.  to  be  falsely  ascribed  to  this  au- 
thor. 

The  Roman  empire  beginning  now  to  be 
oppressed  by  the  barbarians,  and  sunk  in 
gross  superstition,  learning  of  all  kinds  de- 
creased ; and  when  the  empire  was  totally 
overwhelmed  by  those  barbarous  nations,  eve- 
ry appearance  of  science  was  almost  extin- 
guished in  Europe.  The  only  remains  of  it 
were  among  the  Arabians  in  Spain  and  in 
Asia. — The  Saracens  who  came  into  Spain, 
destroyed  at  first  all  the  Greek  books  which 
the  Vandals  had  spared:  but  though  their 
government  was  in  a constant  struggle  and 
fluctuation  during  800  years  before  they 
were  driven  out,  they  received  a taste  for 
learning  from  their  countrymen  of  the  east ; 
several  of  their  princes  encouraged  liberal  stu- 
dies ; public  schools  were  set  up  at  Cordova, 
Toledo,  and  other  towns,  and  translations  of 


History  of  Anatomy . 


19 


the  Greeks  into  the  Arabic  were  universally  in 
the  hands  of  their  teachers. 

Thus  was  the  learning  of  the  Grecians  trans- 
ferred to  the  Arabians.  But  though  they  had 
so  good  a foundation  to  build  upon,  this  art 
was  never  improved  while  they  were  masters 
of  the  world : for  they  were  satisfied  with 

commenting  upon  Galen ; and  seem  to  have 
made  no  dissection  of  human  bodies. 

Abdollaliph,  who  was  himself  a teacher  of 
anatomy,  a man  eminent  in  his  time  (at  and 
before  1203)  for  his  learning  and  curiosity  ; a 
great  traveller,  who  had  been  bred  at  Bagdad, 
and  had  seen  many  of  the  great  cities  and 
principal  places  for  study  in  the  Saracen  em- 
pire ; who  had  a favourable  opinion  of  origin- 
al observation,  in  opposition  to  book-learning  ; 
who  boldly  corrected  some  of  Galen’s  errors, 
and  was  persuaded  that  many  more  might  be 
detected ; this  man,  we  say,  never  made  or 
saw,  or  seemed  to  think  of  a human  dissec- 
tion. He  discovered  Galen’s  errors  in  the  oste- 
ology, by  going  to  burying-grounds,  with  his 
students  and  others,  where  he  examined  and 
demonstrated  the  bones  ; he  earnestly  recom- 
mended that  method  of  study,  in  preference 
even  to  the  reading  of  Galen,  and  thought  that 
many  farther  improvements  might  be  made ; 
yet  he  seemed  not  to  have  an  idea  that  a fresh 
subject  might  be  dissected  with  that  view. 

Perhaps  the  Jewish  tenets,  which  the  Ma- 
hometans adopted,  about  uncleanliness  and 
pollution,  might  prevent  their  handling  dead 
bodies  ; or  their  opinion  of  what  was  suppos- 


20 


History  of  Anatomy. 


ed  to  pass  between  an  angel  and  the  dead 
person,  might  make  them  think  disturbing  the 
dead  highly  sacrilegious.  Such,  however,  as 
Arabian  learning  was,  for  many  ages  together 
there  was  hardly  any  other  in  all  the  western 
countries  of  Europe.  It  was  introduced  by 
the  establishment  of  the  Saracens  in  Spain 
in  711,  and  kept  its  ground  till  the  restora- 
tion of  learning  in  the  end  of  the  15th  centu- 
ry. The  state  of  anatomy  in  Europe,  in  the 
times  of  Arabian  influence,  may  be  seen  by 
reading  a very  short  system  of  anatomy  drawn 
up  by  Mundinus,  in  the  year  1315.  It  was 
extracted  principally  from  what  the  Arabians 
had  preserved  of  Galen’s  doctrine  ; and,  rude 
its  it  is,  in  that  age,  it  was  judged  to  be  so 
masterly  a performance,  that  it  was  ordered 
by  a public  decree,  that  it  should  be  read  in  all 
the  schools  of  Italy  ; and  it  actually  continu- 
ed to  be  almost  the  only  book  which  was 
read  upon  the  subject  for  above  200  years. 
Cortesius  gives  him  the  credit  of  being  the 
great  restorer  of  anatomy,  and  the  first  who 
dissected  human  bodies  among  the  moderns. 

A general  prejudice  against  dissection,  how- 
ever, prevailed  till  the  16th  century.  The 
emperor  Charles  V.  ordered  a consultation  to 
be  held  by  the  divines  of  Salamanca,  in  order 
to  determine  whether  or  not  it  was  lawful  in 
point  of  conscience  to  dissect  a dead  body. 
In  Muscovy,  till  very  lately,  both  anatomy 
and  the  use  of  skeletons  were  forbidden,  the 
first  as  inhuman,  and  the  latter  as  subservi- 
ent to  witchcraft. 


History  of  Anatomy. 


21 


In  the  beginning  of  the  1 5th  century,  learn- 
ing revived  considerably  in  Europe,  and  par- 
ticularly physic,  by  means  of  copies  of  the 
Greek  authors  brought  from  the  sack  of  Con- 
stantinople ; after  which  the  number  of  anato- 
mists and  anatomical  books  increased  to  a pro- 
digious degree. — The  Europeans  becoming 
thus  possessed  of  the  ancient  Greek  fathers 
of  medicine,  were  for  a long  time  so  much 
occupied  in  correcting  the  copies  they  could 
obtain,  studying  the  meaning,  and  comment- 
ing upon  them,  that  they  attempted  nothing 
of  their  own,  especially  in  anatomy. 

And  here  the  late  Dr.  Hunter  introduces 
into  the  annals  of  this  art,  a genius  of  the 
first  rate,  Leonardo  da  Vinci,  who  had  been 
formerly  overlooked,  because  he  was  of  ano- 
ther profession,  and  because  he  published  no- 
thing upon  the  subject.  He  is  considered  by 
the  Doctor  as  by  far  the  best  anatomist  and 
physiologist  of  his  time  ; and  was  certainly  the 
first  man  we  know  of  who  introduced  the  prac- 
tice of  making  anatomical  drawings. 

Vassere,  in  his  lives  of  the  painters,  speaks 
of  Leonardo  thus,  after  telling  us  that  he  had 
composed  a book  of  the  anatomy  of  a horse, 
for  his  own  study : “ He  afterwards  applied 

himself  with  more  diligence  to  the  human  an- 
atomy ; in  which  study  he  reciprocally  receiv- 
ed and  communicated  assistance  to  Marc.  An- 
tonio della  Torre,  an  excellent  philosopher, 
who  then  read  lectures  in  Pavia,  and  wrote 
upon  this  subject ; and  who  was  the  first,  as  I 
have  heard,  who  began  to  illustrate  medicine 


22  History  of  Anatomy. 

from  the  doctrine  of  Galen,  and  to  give  true 
light  to  anatomy,  which  till  that  time  had  been 
involved  in  clouds  of  darkness  and  ignorance. 
In  this  he  availed  himself  exceedingly  of  the 
genius  and  labour  of  Leonardo,  who  made  a 
book  of  studies,  drawn  with  red  chalk,  and 
touched  with  a pen,  with  great  diligence,  of 
such  subjects  as  he  had  himself  dissected ; 
where  he  made  all  the  bones,  and  to  those  he 
joined,  in  their  order,  all  the  nerves,  and  co- 
vered them  with  the  muscles.  And  concern- 
ing those,  from  part  to  part,  he  wrote  remarks 
in  letters  of  an  ugly  form,  which  are  written 
by  the  left  hand,  backwards,  and  not  to  be  un- 
derstood but  by  those  who  know  the  method 
of  reading  them  ; for  they  are  not  to  be  read 
without  a looking-glass.  Of  these  papers  of 
the  human  anatomy,  there  is  a great  part  in 
the  possession  of  M.  Francesco  da  Melzo,  a 
Milanese  gentleman,  who,  in  the  time  of  Le- 
onardo, was  a most  beautiful  boy,  and  much 
beloved  by  him,  as  he  is  now  a beautiful  and 
genteel  old  man,  who  reads  those  writings, 
and  carefully  preserves  them,  as  precious  re- 
licks, together  with  the  portrait  of  Leonardo, 
of  happy  memory.  It  appears  impossible  that 
that  divine  spirit  should  reason  so  well  upon 
the  arteries,  and  muscles,  and  nerves,  and 
veins  ; and  with  such  diligence  of  every  thing, 
&c.  &c.” 

Those  very  drawings  and  the  writings  are 
happily  found  to  be  preserved  in  his  Britan- 
nic Majesty’s  great  collection  of  original  draw- 
ings, where  the  Doctor  was  permitted  to  exa- 


History  of  Anatomy. 


23 


mine  them  ; and  his  sentiments  upon  the  oc- 
casion he  thus  expresses  : “ I expected  to  see 
little  more  than  such  designs  in  anatomy,  as 
might  be  useful  to  a painter  in  his  own  pro- 
fession ; but  I saw,  and  indeed  with  astonish- 
ment, that  Leonardo  had  been  a general  and  a 
deep  student.  When  I consider  what  pains  he 
has  taken  upon  every  part  of  the  body,  the  su- 
periority of  his  universal  genius,  his  particular 
excellence  in  mechanics  and  hydraulics,  and 
the  attention  with  which  such  a man  would  ex- 
amine and  see  objects  which  he  was  to  draw, 
I am  fully  persuaded  that  Leonardo  was  the 
best  anatomist  at  that  time  in  the  world.  We 
must  give  the  15th  century  the  credit  of  Leo- 
nardo’s anatomical  studies,  as  he  was  55  years 
of  age  at  the  close  of  that  century.’’ 

In  the  beginning  of  the  16th  century,  Achil- 
linus  and  Benedictus,  but  particularly  Beren- 
garius  and  Massa,  followed  out  the  improve- 
ment of  anatomy  in  Italy,  where  they  taught 
it,  and  published  upon  the  subject.  These 
first  improvers  made  some  discoveries  from 
their  own  dissections  : but  it  is  not  surprising 
that  they  should  have  been  diffident  of  them- 
selves, and  have  followed  Galen  almost  blind- 
ly, when  his  authority  had  been  so  long  estab- 
lished, and  when  the  enthusiasm  for  Greek 
authors  was  rising  to  such  a pitch. 

Soon  after  this,  we  may  say  about  the  year 
1540,  the  great  Vesalius  appeared.  He  was 
studious,  laborious,  and  ambitious.  From 
Brussels,  the  place  of  his  birth,  he  went  to 
Louvain,  and  thence  to  Pans,  where  anatomy 


24 


History  of  Anatomy. 


was  not  yet  making  a considerable  figure,  and 
then  to  Louvain  to  teach ; from  which  place, 
very  fortunately  for  his  reputation,  he  was  call- 
ed to  Italy,  where  he  met  with  every  oppor- 
tunity that  such  a genius  for  anatomy  could 
desire,  that  is,  books,  subjects,  and  excellent 
draughtsmen.  He  was  equally  laborious  in 
reading  the  ancients,  and  in  dissecting  bodies. 
And  in  making  the  comparison,  he  could  not 
but  see,  that  there  was  great  room  for  improve- 
ment, and  that  many  of  Galen’s  descriptions 
were  erroneous.  When  he  was  but  a young 
man,  he  published  a noble  system  of  anatomy, 
illustrated  with  a great  number  of  elegant  fi- 
gures.— In  this  work  he  found  so  many  occa- 
sions of  correcting  Galen,  that  his  contempo- 
raries, partial  to  antiquity,  and  jealous  of  his 
reputation,  complained  that  he  carried  his  turn 
for  improvement  and  criticisms  to  licentious- 
ness. The  spirit  of  opposition  and  emulation 
was  presently  roused ; and  Sylvius  in  France, 
Columbus,  Fallopius,  and  Eustachius  in  Italy, 
who  were  all  in  high  anatomical  reputation 
about  the  middle  of  this  16th  century,  endea- 
voured to  defend  Galen  at  the  expense  of  Ve- 
salius.  In  their  disputes  they  made  their  ap- 
peals to  the  human  body : and  thus  in  a few 
years  the  art  was  greatly  improved.  And  Ve- 
salius  being  detected  in  the  very  fault  which 
he  condemned  in  Galen,  to  wit,  describing 
from  the  dissections  of  brutes,  and  not  of  the 
human  body,  it  exposed  so  fully  that  blunder 
of  the  older  anatomists,  that  in  succeeding 
times  there  has  been  little  reason  for  such 


History  of  Anatomy . 


25 


complaint. — Besides  the  above,  he  published 
several  other  anatomical  treatises.  He  has 
been  particularly  serviceable  by  imposing 
names  on  the  muscles,  most  of  which  are  re- 
tained to  this  day.  Formerly  they  were  dis- 
tinguished by  numbers,  which  were  different- 
ly applied  by  almost  every  author. 

In  1561,  Gabriel  Fallopius,  professor  of 
anatomy  at  Padua,  published  a treatise  of  ana- 
tomy under  the  title  of  Observations  Anatomi- 
es. This  was  designed  as  a supplement  to 
Vesalius;  many  of  whose  descriptions  he  cor- 
rects, though  he  always  makes  mention  of  him 
in  an  honourable  manner.  Fallopius  made 
many  great  discoveries,  and  his  book  is  well 
worth  the  perusal  of  every  anatomist. 

In  1563,  Bartholomseus  Eustachius  pub- 
lished his  Opuscula  Anatomica  at  Venice,  which 
have  ever  since  been  justly  admired  for  the  ex- 
actness of  the  descriptions,  and  the  discove- 
ries contained  in  them.  He  published  after- 
wards some  other  pieces,  in  which  there  is  lit- 
tle of  anatomy  ; but  never  published  the  great 
work  he  had  promised,  which  was  to  be  adorn- 
ed with  copperplates  representing  all  the  parts 
of  the  human  body.  These  plates,  after  lying 
buried  in  an  old  cabinet  for  upwards  of  150 
years,  were  at  last  discovered  and  published 
in  the  year  1714,  by  Lancisi  the  pope’s  phy- 
sician ; who  added  a short  explicatory  text,  be- 
cause Eustachius’s  own  writing  could  not  be 
found. 

From  this  time  the  study  of  anatomy  gradu- 
ally diffused  itself  over  Europe  ; insomuch  that 

D 


26 


History  of  Anatomy. 


for  the  last  hundred  years  it  has  been  daily  im- 
proving by  the  labour  of  a number  of  profes- 
sed anatomists  almost  in  every  country  of  Eu- 
rope. 

We  may  form  a judgment  about  the  state  of 
anatomy  even  in  Italy,  in  the  beginning  of  the 
17th  century,  from  the  information  of  Corte- 
sius.  He  had  been  professor  of  anatomy  at 
Bologna,  and  was  then  professor  of  medicine 
at  Massana ; where,  though  he  had  a great 
desire  to  improve  himself  in  the  art,  and  to  fi- 
nish a treatise  which  he  had  begun  on  practi- 
cal anatomy,  in  24  years  he  could  twice  only 
procure  an  opportunity  of  dissecting  a human 
body,  and  then  it  was  with  difficulties  and  in 
hurry ; whereas  he  had  expected  to  have  done 
so,  he  says,  once  every  year , according  to  the 
custom  in  the  famous  academies  oj  Italy. 

In  the  very  end  of  the  16th  century,  the 
great  Harvey,  as  was  the  custom  of  the  times, 
went  to  Italy  to  study  medicine  ; for  Italy  was 
still  the  favourite  seat  of  the  arts : And  in  the 
very  beginning  of  the  17th  century,  soon  after 
Harvey’s  return  to  England,  his  master  in  ana- 
tomy, Fabricius  ab  Aquapendente,  published 
an  account  of  the  valves  in  the  veins,  which 
he  had  discovered  many  years  before,  and  no 
doubt  taught  in  his  lectures  when  Harvey  at- 
tended him. 

This  discovery  evidently  affected  the  estab- 
lished doctrine  of  all  ages,  that  the  veins  car- 
ried the  blood  from  the  liver  to  all  parts  of  the 
body  for  nourishment.  It  set  Harvey  to  work 
upon  the  use  of  the  heart  and  vascular  systems 


History  of  Anatomy. 


27 


in  animals  ; and  in  the  course  of  some  years 
he  was  so  happy  as  to  discover,  and  to  prove 
beyond  all  possibility  of  doubt,  the  circulation 
of  the  blood.  He  taught  his  new  doctrine  in 
his  lectures  about  the  year  1616,  and  printed 
it  in  1628. 

It  was  by  far  the  most  important  step  that 
had  been  made  in  the  knowledge  of  animal  bo- 
dies in  any  age.  It  not  only  reflected  useful 
lights  upon  what  had  been  already  found  out 
in  anatomy,  but  also  pointed  out  the  means  of 
further  investigation.  And  accordingly  we  see, 
that  from  Harvey  to  the  present  time,  anato- 
my has  been  so  much  improved,  that  we  may 
reasonably  question  if  the  ancients  have  been 
further  outdone  by  the  moderns  in  any  other 
branch  of  knowledge.  From  one  day  to  ano- 
ther there  has  been  a constant  succession  of 
discoveries,  relating  either  to  the  structure  or 
functions  of  our  body  ; and  new  anatomical 
processes,  both  of  investigation  and  demon- 
stration, have  been  daily  invented.  Many 
parts  of  the  body,  which  wTere  not  known  in 
Harvey’s  time,  have  since  then  been  brought 
to  light : and  of  those  which  were  known,  the 
internal  composition  and  functions  remained 
unexplained  ; and  indeed  must  have  remained 
unexplicable  without  the  knowledge  of  the  cir- 
culation. 

Harvey’s  doctrine  at  first  met  with  conside- 
rable opposition  ; but  in  the  space  of  about  20 
years  it  was  so  generally  and  so  warmly  em- 
braced, that  it  was  imagined  every  thing  in 
physic  would  be  explained.  But  time  and  ex- 


28 


History  of  Anatomy. 


perience  have  taught  us,  that  we  still  are,  and 
probably  must  long  continue  to  be,  very  igno- 
rant ; and  that  in  the  study  of  the  human  body, 
and  of  its  diseases,  there  will  always  be  an 
extensive  field  for  the  exercise  of  sagacity. 

After  the  discovery  and  knowledge  of  the 
circulation  of  the  blood,  the  next  question 
would  naturally  have  been  about  the  passage 
and  route  of  the  nutritious  part  of  the  food  or 
chyle  from  the  bowels  to  the  blood-vessels : 
And,  by  good  fortune,  in  a few  years  after 
Harvey  had  made  his  discovery,  Asellius,  an 
Italian  physician,  found  out  the  lacteals,  or 
vessels  which  carry  the  chyle  from  the  intes- 
tines ; and  printed  his  account  of  them,  with 
coloured  prints,  in  the  year  1627,  the  very 
year  before  Harvey’s  book  came  out. 

For  a number  of  years  after  these  two  pub- 
lications, the  anatomists  in  all  parts  of  Europe 
were  daily  opening  living  dogs,  either  to  see 
the  lacteals  or  to  observe  the  phenomena  of 
the  circulation.  In  making  an  experiment  of 
this  kind,  Pecquet  in  France  was  fortunate 
enough  to  discover  the  thoracic  duct,  or  com- 
mon trunk  of  all  the  lacteals,  which  conveys 
the  chyle  into  the  subclavian  vein.  He  print- 
ed his  discovery  in  the  year  1651.  And  now 
the  lacteals  having  been  traced  from  the  intes- 
tines to  the  thoracic  duct,  and  that  duct  having 
been  traced  to  its  termination  in  a blood-ves- 
sel, the  passage  of  the  chyle  was  completely 
made  out. 

The  same  practice  of  opening  living  animals 
furnished  occasions  of  discovering  the  lympha- 


History  of  Anatomy. 


29 


tic  vessels.  This  good  fortune  fell  to  the 
lot  of  Rudbec  first,  a young  Swedish  anato- 
mist ; and  then  to  Thomas  Bartholine,  a Da- 
nish anatomist,  who  was  the  first  who  appear- 
ed in  print  upon  the  lymphatics.  His  book 
came  out  in  the  year  16  53,  that  is,  two  years 
after  that  of  Pecquet.  And  then  it  was  very  evi- 
dent that  they  had  been  seen  before  by  Dr.  Hig- 
more  and  others,  who  had  mistaken  them  for 
lacteals.  But  none  of  the  anatomists  of  those 
times  could  make  out  the  origin  of  the  lym- 
phatics, and  none  of  the  physiologists  could 
give  a satisfactory  account  of  their  use. 

The  circulation  of  the  blood,  and  the  pas- 
sage of  the  chyle  having  been  satisfactorily 
traced  out  in  full-grown  animals,  the  anato- 
mists were  naturally  led  next  to  consider  how 
these  animal  processes  were  carried  on  in 
the  child  while  in  the  womb  of  the  mother. 
Accordingly  the  male  and  female  organs,  the 
appearances  and  contents  of  the  pregnant  ute- 
rus, the  incubated  egg,  and  every  phenome- 
non which  could  illustrate  generation,  became 
the  favourite  subject,  for  about  30  years,  with 
the  principal  anatomists  of  Europe. 

Thus  it  would  appear  to  have  been  in  theo- 
ry : but  Dr.  Hunter  believes,  that  in  fact,  as 
Harvey’s  master  Fabricius  laid  the  foundation 
for  the  discovery  of  the  circulation  of  the 
blood  by  teaching  him  the  valves  of  the  veins, 
and  thereby  inviting  him  to  consider  that  sub- 
ject; so  Fabricius  by  his  lectures,  and  by  his 
elegant  work  He  formato  fcetu , et  de formatione 
ovi  et  pulli , probably  made  that  likewise  a fa- 


30 


History  of  Anatomy. 


vourite  subject  with  Dr.  Harvey.  But  whe- 
ther he  took  up  the  subject  of  generation  in 
consequence  of  his  discovery  of  the  circula- 
tion, or  was  led  to  it  by  his  honoured  master 
Fabricius,  he  spent  a great  deal  of  his  time 
in  the  inquiry  ; and  published  his  observations 
in  a book  De  generations  animalium , in  the 
year  16  51,  that  is,  six  years  before  his  death. 

In  a few  years  after  this,  Swammerdam,  Van 
Horn,  Steno,  and  De  Graaf,  excited  great  at- 
tention to  the  subject  of  generation,  by  their 
supposed  discovery  that  the  females  of  vivipa- 
rous animals  have  ovaria,  that  is,  clusters  of 
eggs  in  their  loins,  like  oviparous  animals  ; 
which,  when  impregnated  by  the  male,  are 
conveyed  into  the  uterus;  so  that  a child  is 
produced  from  an  egg  as  well  as  a chick  ; with 
this  difference,  that  one  is  hatched  within,  and 
the  other  without,  the  body  of  the  mother. 

Malpighi,  a great  Italian  genius,  some  time 
after,  made  considerable  advances  upon  the 
subject  of  generation.  He  had  the  good  for- 
tune to  be  the  first  who  used  magnifying  glass- 
es with  address  in  tracing  the  first  appearances 
in  the  formation  of  animals.  Fie  likewise  made 
many  other  observations  and  improvements  in 
the  minutia  of  anatomy  by  his  microscopical  la- 
bours, and  by  cultivating  comparative  anato- 
my. 

This  distinguished  anatomist  gave  the  first 
public  specimen  of  his  abilities,  by  printing  a 
dissertation  on  the  lungs  anno  1661 ; a period 
so  remarkable  for  the  study  of  nature,  that  it 
would  be  injustice  to  pass  it  without  particular 
notice. 


History  of  Anatomy . 


31 


At  the  same  time  flourished  Laurentius 
Bellirras  at  Florence,  and  was  the  first  who 
introduced  mathematical  reasoning  in  physic. 
In  1662,  Simon  Pauli  published  a treatise  De 
albanclis  cssibus.  Fie  had  long  been  admired 
for  the  white  skeletons  he  prepared ; and  at 
last  discovered  his  method,  which  was  by  ex- 
posing the  bones  all  winter  to  the  weather. 

Johannes  Swammerdam  of  Amsterdam  also 
published  some  anatomical  treatises  ; but  was 
most  remarkable  for  his  knowledge  of  pre- 
serving the  parts  of  bodies  entire  for  many 
years,  by  injecting  their  vessels.  He  also 
published  a treatise  on  respiration;  wherein 
he  mentioned  his  having  figures  of  all  the 
parts  of  the  body  as  big  as  the  life,  cut  in 
copper,  which  he  designed  to  publish,  with  a 
complete  systems  of  anatomy.  These,  howe- 
ver, were  never  made  public  by  Swammerdam; 
but,  in  1683,  Gothofridus  Bidloo,  professor 
of  anatomy  at  Leyden,  published  a work  en- 
titled Anatomia  corporis  hurnani , where  all  the 
parts  were  delineated  in  very  large  plates  al- 
most as  big  as  the  life.  Mr.  Cowper,  an  Eng- 
lish surgeon,  bought  300  copies  of  these  fi- 
gures ; and  in  1698,  published  them  with  an 
English  text,  quite  different  from  Bidloo’s  La- 
tin one  ; to  which  were  added  letters  in  Bid- 
loo’s figures,  and  some  few  figures  of  Mr. 
Cowper’s  own.  To  this  work  Cowper’s  name 
was  prefixed,  without  the  least  mention  of  Bid- 
loo, except  on  purpose  to  confute  him.  Bid- 
loo immediately  published  a very  ill-natured 
pamphlet,  called  GaHelmus  Cowperus  citatus 


23  History  of  Anatomy. 

coram  tribunal i;  appealing  to  the  Royal  Soci- 
ety, how  far  Cowper  ought  to  be  punished 
as  a plagiary  of  the  worst  kind,  and  endea- 
vouring to  prove  him  an  ignorant  deceitful 
fellow.  Cowper  answered  him  in  his  own 
style,  in  a pamphlet  called  his  V indicia ; en- 
deavouring to  prove,  either  that  Bidloo  did 
not  understand  his  own  tables,  or  that  they 
were  none  of  his.  It  was  even  alleged  that 
those  were  the  tables  promised  by  Swam- 
merdam, and  which  Bidloo  had  got  from  his 
widow.  This,  however,  appears  to  have  been 
only  an  invidious  surmise,  there  being  un- 
questionable evidence  that  they  were  really 
the  performance  of  Bidloo. 

Soon  after,  Xsbrandus  Biembroeck,  profes- 
sor of  anatomy  at  Utrecht,  began  to  appear 
as  an  author.  His  work  contained  very  little 
original ; but  he  was  at  great  pains  to  collect 
from  others  whatever  was  valuable  in  their 
writings,  and  his  system  was  the  common 
standard  among  anatomical  students  for  ma- 
ny years. 

About  the  same  time,  Antonins  Liewen- 
hoeck  of  Delft,  improved  considerably"  on 
Malpighi’s  use  of  microscopes.  These  two 
authors  took  up  anatomy  where  others  had 
dropt  it ; and,  by  this  new  art,  they  brought 
a number  of  amazing  things  to  light.  They 
discovered  the  red  globules  of  the  blood : 
they  were  enabled  to  see  the  actual  circula- 
tion of  the  blood  in  the  transparent  parts  of 
living  animals,  and  could  measure  the  velo- 
city of  its  motion;  they  discovered  that  the 


History  of  Anatomy. 


33 


arteries  and  veins  had  no  intermediate  cells 
or  spungy  substance,  as  Harvey  and  all  the 
preceding  anatomists  had  supposed,  but  com- 
municated one  with  the  other  by  a continua- 
tion of  the  same  tube. 

Liewenhoeck  was  in  great  fame  likewise 
for  his  discovery  of  the  animalcula  in  the  se- 
men. Indeed  there  was  scarcely  a part  of  the 
body,  solid  or  fluid,  which  escaped  his  examina- 
tion ; and  he  almost  every  where  found,  that 
what  appeared  to  the  naked  eye  to  be  rude  un- 
digested matter,  was  in  reality  a beautiful  and 
regular  compound. 

After  this  period,  Nuck  added  to  our  know- 
ledge of  the  absorbent  system  already  men- 
tioned, by  his  injections  of  the  lymphatic 
glands ; Ruysch,  by  his  description  of  the 
valves  of  the  lymphatic  vessels;  and  Dr. 
Meckel,  by  his  accurate  account  of  the  whole 
system,  and  by  tracing  those  vessels  in  many 
parts  where  they  had  not  before  been  de- 
scribed. 

Besides  these  authors,  Drs.  Hunter  and 
Monro  have  called  the  attention  of  the  pub- 
lic to  this  part  of  anatomy,  in  their  contro- 
versy concerning  the  discovery  of  the  office 
of  the  lymphatics. 

When  the  lymphatic  vessels  were  first  seen 
and  traced  into  the  thoracic  duct,  it  was  natu- 
ral for  anatomists  to  suspect,  that  as  the  lac- 
teals  absorbed  from  the  cavity  of  the  intes- 
tines, the  lymphatics,  which  are  similar  in 
figure  and  structure,  might  possibly  do  the 
same  office  with  respect  to  other  parts  of  the 

E 


34 


History  of  Anatomy . 


body : and  accordingly,  Dr.  Glisson,  who 
wrote  in  16  54,  supposes  these  vessels  arose 
from  cavities,  and  that  their  use  was  to  ab- 
sorb ; and  Frederic  Hoffman  has  very  expli- 
citly laid  down  the  doctrine  of  the  lymphatic 
vessels  being  a system  of  absorbents.  But 
anatomists  in  general  have  been  of  a contra- 
ry opinion ; for,  from  experiments,  particular- 
ly such  as  were  made  by  injections,  they  have 
been  persuaded  that  the  lymphatic  vessels  did 
not  arise  from  cavities,  and  did  not  absorb, 
but  were  merely  continuations  from  small  ar- 
teries. The  doctrine,  therefore,  that  the  lym- 
phatics, like  the  lacteals,  were  absorbents,  as 
had  been  suggested  by  Glisson  and  by  Hoff- 
man, has  been  revived  by  Dr.  Hunter  and  Dr. 
Monro,  who  have  controverted  the  experi- 
ments of  their  predecessors  in  anatomy,  and 
have  endeavoured  to  prove  that  the  lympha- 
tic vessels  are  not  continued  from  arteries, 
but  are  absorbents. 

To  this  doctrine,  however,  several  objec- 
tions have  been  started,  particularly  by  Hal- 
ler (Elem.  Phys.  1.  24.  § 2,  3.)  ; and  it  has 
been  found,  that  before  the  doctrine  of  the 
lymphatics  being  a system  of  absorbents  can 
be  established,  it  must  first  be  determined 
whether  this  system  is  to  be  found  in  other 
animals  besides  man  and  quadrupeds.  Mr. 
Hewson  claims  the  merit  of  having  proved 
the  affirmative  of  this  question,  by  discover- 
ing the  lymphatic  system  in  birds,  fish,  and 
amphibious  animals.  See  Phil.  Trans,  vol. 
1-viii.  and  lxix. — And  latterly,  Mr.  Cruikshank 


History  of  Anatomy. 


35 


has  traced  the  ramifications  of  that  system  in 
almost  every  part  of  the  body ; and  from  his 
dissections,  figures  have  been  made  and  lately 
published  to  the  world.  To  Mr.  Sheldon  also 
we  are  much  indebted  for  his  illustration  of 
this  system,  which  promises  to  give  great  sa- 
tisfaction, but  of  which  only  a part  has  yet 
been  published. 

The  gravid  uterus  is  a subject  likewise'* 
which  has  received  considerable  improve- 
ments, particularly  relating  to  one  very  im- 
portant discovery ; viz.  that  the  internal  mem- 
brane of  the  uterus,  which  Dr.  Hunter  has 
named  decidua , constitutes  the  exterior  part 
of  the  secundines  or  after-birth,  and  separates 
from  the  rest  of  the  uterus  every  time  that  a 
woman  either  bears  a child  or  suffers  a mis- 
carriage. This  discovery  includes  another,  to 
wit,  that  the  placenta  is  partly  made  up  of  an 
excrescence  or  efflorescence  from  the  uterus 
itself. 

These  discoveries  are  of  the  utmost  conse- 
quence, both  in  the  physiological  question 
about  the  connection  between  the  mother  and 
child,  and  likewise  in  explaining  the  phenome- 
na of  births  and  abortions,  as  well  as  in  re- 
gulating obstetrical  practice. 

The  anatomists  of  this  century  have  im- 
proved anatomy,  and  have  made  the  study  of 
it  much  more  easy,  by  giving  us  more  correct 
as  well  as  more  numerous  figures.  It  is  amaz- 
ing to  think  of  what  has  been  done  in  that 
time.  We  have  had  four  large  folio  books  of 
figures  of  the  bones,  viz.  Cheselden’s,  Albi- 


36 


History  of  Anatomy. 


nus’s,  Sue’s  and  Trew’s.  Of  the  muscles,  we 
have  had  two  large  folios ; one  from  Cowper, 
which  is  elegant  ; and  one  from  Albinus, 
which,  from  the  accuracy  and  labour  of  the 
work,  we  may  suppose  will  never  be  outdone. 
Of  tiie  blood-vessels  we  have  a large  folio 
from  Dr.  Haller.  We  have  had  one  upon 
the  nerves  from  Dr.  Meckel,  and  another  by 
Dr.  Monro  junior.  We  have  had  Albinus’s, 
Roederer’s,  Jenty’s,  and  Hunter’s  works  up- 
on the  pregnant  uterus;  Weitbrecht  and  Le- 
ber on  the  joints  and  fresh  bones ; Soemer- 
ring  on  the  brain ; Zin  on  the  eye ; Cotunius, 
Meckel  junior,  £*c.  on  the  ear;  Waiterus  on 
the  nerves  of  the  thorax  and  abdomen ; Dr. 
Monro  on  the  bursae  mucosae,  &c. 

It  would  be  endless  to  mention  the  anato- 
mical figures  that  have  been  published  in  this 
century,  of  particular  and  smaller  parts  of  the 
body,  by  Morgagni,  Ruysch,  Valsalva,  Sanc- 
torini,  Heister,  Vater,  Cant,  Zimmerman, 
Waiterus,  and  others. 

Those  elegant  plates  of  the  brain,  howe- 
ver, just  published  by  M.  Vicq.  d’Azyr,  must 
not  pass  without  notice,  especially  as  they 
form  part  of  an  universal  system  of  anatomy 
and  physiology,  both  human  and  comparative, 
proposed  to  be  executed  in  the  same  splendid 
style.  Upon  the  brain  alone  19  folio  plates 
are  employed;  of  which  several  are  coloured. 
The  figures  are  delineated  with  accuracy  and 
clearness  ; but  the  colouring  is  rather  beauti- 
ful than  correct.  Such  parts  of  this  work  as 
may  be  published,  cannot  fad  to  be  equally 


History  of  Anatomy. 


37 


acceptable  to  the  anatomist  and  the  philoso- 
pher; but  the  entire  design  is  apparently  too 
extensive  to  be  accomplished  within  the  peri- 
od of  a single  life.  In  Great  Britain,  also,  a 
very  great  anatomical  work  is  carrying  on  by 
Andrew  Bell,  F.  S.  A.  S.  engraver  to  his 
Royal  Highness  the  Prince  of  Wales,  wdth 
the  approbation  of  Dr.  Monro,  and  under  the 
inspection  of  his  very  ingenious  assistant  Mr. 
Fyfe.  It  is  to  compose  a complete  illustra- 
tion, both  general  and  particular,  of  the  hu- 
man body,  by  a selection  from  the  best  plates 
of  all  the  greatest  anatomists,  as  well  foreign 
as  British,  exhibiting  the  latest  discoveries  in 
the  science,  and  accompanied  with  copious  ex- 
planations. The  whole  number  of  plates 
mentioned  in  the  Prospectus  is  240,  of  which 
152  are  already  done ; all  in  royal  folio, 

To  the  foreign  treatises  already  mentioned 
may  be  added  those  recently  published  by 
Sabbatier  and  Plenck  on  anatomy  in  general. 
In  Great-Britain,  the  writings  of  Keil,  Doug- 
las, Cheselden,  the  first  Monro,  Winslow, 
£kc.  are  too  well  known  to  need  description. 
The  last  of  these  used  to  be  recommended  as 
a standard  for  the  students  of  anatomy:  but 
it  has  of  late  given  place  to  a more  accu- 
rate and  comprehensive  system,  in  three  vo- 
lumes, published  by  Mr.  Elliot  of  Edinburgh, 
upon  a plan  approved  of  by  Dr.  Monro, 
and  executed  by  Mr.  Fyfe.  Dr.  Simmons  of 
London  has  also  obliged  the  world  with  an 
excellent  system  of  anatomy ; and  another 
work,  under  the  title  of  “ Elements  of  Ana- 


38 


History  of  Anatomy. 


tomy  and  the  Animal  Oeconomy:”  in  which 
the  subjects  are  treated  with  uncommon  ele- 
gance and  perspicuity. 

In  the  latter  part  of  the  last  century,  ana- 
tomy made  two  great  steps,  by  the  invention 
of  injections,  and  the  method  of  making  what 
we  commonly  call  preparations.  These  two 
modern  arts  have  really  been  of  infinite  use 
to  anatomy;  and  besides  have  introduced  an 
elegance  into  our  administrations,  which  in 
former  times  could  not  have  been  supposed 
to  be  possible.  They  arose  in  Holland  un- 
der Swammerdam  and  Ruysch,  and  after- 
wards in  England  under  Cowper,  St.  Andre, 
and  others,  where  they  have  been  greatly  im- 
proved. 

The  anatomists  of  former  ages  had  no  other 
knowledge  of  the  blood-vessels,  than  what 
they  were  able  to  collect  from  laborious  dis- 
sections, and  from  examining  the  smaller 
branches  of  them,  upon  some  lucky  occa- 
sion, when  they  were  found  more  than  com- 
monly loaded  with  red  blood.  But  filling 
the  vascular  system  with  a bright  coloured 
wax,  enables  us  to  trace  the  large  vessels 
with  great  ease,  renders  the  smaller  much 
more  conspicuous,  and  makes  thousands  of 
the  very  minute  ones  visible,  which  from  their 
delicacy,  and  the  transparency  of  their  natu- 
ral contents,  are  otherwise  imperceptible. 

The  modern  art  of  corroding  the  fleshy 
parts  with  a menstruum,  and  of  leaving  the 
moulded  wax  entire,  is  so  exceedingly  useful, 
and  at  the  same  time  so  ornamental,  that  it 


History  of  Anatomy.  39 

does  great  honour  to  the  ingenious  inventor 
Dr.  Nicholls. 

The  wax-work  art  of  the  moderns  might  de- 
serve notice  in  any  history  of  anatomy,  if  the 
masters  in  that  way  had  not  been  so  careless 
in  their  imitation.  Many  of  the  wax-figures 
are  so  tawdry  with  a show  of  unnatural  co- 
lours, and  so  very  incorrect  in  the  circum- 
stances of  figure,  situation,  and  the  like,  that 
though  they  strike  a vulgar  eye  with  admira- 
tion, they  must  appear  ridiculous  to  an  ana- 
tomist. But  those  figures  which  are  cast  in 
wax,  plaster,  or  lead,  from  the  real  subject, 
and  which  of  late  years  have  been  frequently 
made,  are,  of  course,  very  correct  in  all  the 
principal  parts,  and  may  be  considered  as  no 
insignificant  acquisition  to  modern  anatomy. 
The  proper,  or  principal  use  of  this  art  is,  to 
preserve  a very  perfect  likeness  of  such  sub- 
jects as  we  but  seldom  can  meet  with,  or  can- 
not well  preserve  in  a natural  state  ; a subject 
in  pregnancy,  for  example. 

The  modern  improved  methods  of  preserv- 
ing animal  bodies,  or  parts  of  them,  has  been 
of  the  greatest  service  to  anatomy ; especially 
in  saving  the  time  and  labour  of  the  anato- 
mist in  the  nicer  dissections  of  the  small 
parts  of  the  body.  For  now,  whatever  he 
has  prepared  with  care,  he  can  preserve;  and 
the  object  is  ready  to  be  seen  at  any  time. 
And  in  the  same  manner  he  can  preserve  ana- 
tomical curiosities,  or  rarities  of  every  kind  ■ 
such  as,  parts  that  are  uncommonly  formed  ; 
parts  that  are  diseased ; the  parts  of  the  preg- 


40 


Introduction  to  Anatomy. 


nant  uterus  and  its  contents.  Large  collec- 
tions of  such  curiosities,  which  modern  ana- 
tomists are  striving  almost  every  where  to 
procure,  are  of  infinite  service  to  the  art,  es- 
pecially in  the  hands  of  teachers.  They  give 
students  clear  ideas  about  many  things  which 
it  is  very  essential  to  know,  and  yet  which  it 
is  impossible  that  a teacher  should  be  able  to 
show  otherwise,  were  he  ever  so  well  suppli- 
ed with  fresh  subjects. 


2.  View  of  the  Subject  in  general , and  Plan  of 
the  following  Treatise. 

\ 

THE  etymology  of  the  word  anatomy , as 
above  given,  implies  simply  dissection  ; but  by 
this  term  something  more  is  usually  under- 
stood. 

It  is  every  day  made  use  of  to  express  a 
knowledge  of  the  human  body  ; and  a person 
who  is  said  to  understand  anatomy,  is  sup- 
posed to  be  conversant  with  the  structure  and 
arrangement  of  the  different  solid  parts  of  the 
body. 

It  is  commonly  divided  into  Anatomy , pro- 
perly so  called  ; and  Comparative  Anatomy : 
the  first  of  these  is  confined  solely  to  the  hu- 
man body ; the  latter  includes  all  animals,  so 
far  as  a knowledge  of  their  structure  may  tend 
to  perfect  our  ideas  of  the  human  body. 


Introduction  to  Anatomy.  41 

The  term  anatomy  may  also  have  another 
and  more  extensive  signification : it  may  be 
employed  to  express  not  only  a knowledge  of 
the  structure  and  disposition  of  the  parts  but 
likewise  of  their  ceconomy  and  use.  Consider- 
ed in  this  light,  it  will  seldom  fail  to  excite  the 
curiosity  of  people  of  taste,  as  a branch  of 
philosophy  ; since  if  it  is  pleasing  to  be  ac- 
quainted with  the  structure  of  the  body,  it  is 
certainly  more  so  to  discover  all  the  springs 
which  give  life  and  motion  to  the  machine, 
and  to  observe  the  admirable  mechanism  by 
which  so  many  different  functions  are  exe- 
cuted. 

Astronomy  and  anatomy,  as  Dr.  Hunter, 
after  Fontenelle,  observes,  are  the  studies 
which  present  us  with  the  most  striking  view 
of  the  two  greatest  attributes  of  the  Supreme 
Being.  The  first  of  these  fills  the  mind  with 
the  idea  of  his  immensity,  in  the  largeness, 
distances,  and  number  of  the  heavenly  bodies  ; 
the  last,  astonishes  with  his  intelligence  and 
art  in  the  variety  and  delicacy  of  animal  me- 
chanism. 

The  human  body  has  been  commonly 
enough  known  by  the  name  of  ?nicrocos?nus , 
or  the  little  world  ; as  if  it  did  not  differ  so 
much  from  the  universal  system  of  nature  in 
the  symmetry  and  number  of  its  parts  as  in 
their  size. 

Galen’s  excellent  treatise  De  usu  partium , 
was  composed  as  a prose  hymn  to  the  Crea- 
tor ; and  abounds  with  as  irresistible  proofs 
of  a supreme  Cause  and  governing  Provi- 


42 


Introduction  to  Anatomy. 


dence,  as  we  find  in  modern  physico-theology. 
And  Cicero  dwells  more  on  the  structure  and 
ceconomy  of  animals  than  on  all  the  produc- 
tions of  nature  besides,  when  he  wants  to 
prove  the  existence  of  the  gods  from  the  or- 
der and  beauty  of  the  universe.  He  there 
takes  a survey  of  the  body  of  man  in  a most 
elegant  synopsis  of  anatomy,  and  concludes 
thus:  u Quibus  rebus  expositis,  satis  docuisse 
videor,  hominis  natura,  quanto  omnes  anteiret 
animantes.  Ex  quo  debet  intelligi,  nec  figu- 
ram  situmque  membrorum,  nec  ingenii  men- 
tisque  vim  talem  effici  potuisse  fortuna.” 

The  satisfaction  of  mind  which  arises  from 
the  study  of  anatomy,  and  the  influence  which 
it  must  naturally  have  upon  our  minds  as  phi- 
losophers, cannot  be  better  conveyed  than  by 
the  following  passage  from  the  same  author : 
“ Quae  contuens  animus,  accepit  ab  his  cogni- 
tionem  deorum,  ex  qua  oritur  pietas : cui  con- 
juncta  justitia  est,  reliquasque  virtutes : ex 

quibus  vita  beata  exsistit,  par  et  similes  deo- 
rum, nulla  alia  re  nisi  immortalitate,  quae  ni- 
hil ad  bene  vivendum  pertinet,  cedens  cceles- 
tibus.” 

It  would  be  endless  to  quote  the  animated 
passages  of  this  sort  which  are  to  be  found  in 
the  physicians,  philosophers,  and  theologists, 
who  have  considered  the  structure  and  func- 
tions of  animals  with  a view  towards  the  Cre- 
ator. It  is  a view  which  must  strike  one  with 
a most  awful  conviction.  Who  can  know  and 
consider  the  thousand  evident  proofs  of  the  as- 
tonishing art  of  the  Creator,  in  forming  and 


Introduction  to  Anatomy . 43 

sustaining  an  animal  body  such  as  ours,  with- 
out feeling  the  most  pleasant  enthusiasm  ? Can 
we  seriously  reflect  upon  this  awful  subject, 
without  being  almost  lost  in  adoration  ? with- 
out longing  for  another  life  after  this,  in  which 
we  may  be  gratified  with  the  highest  enjoy- 
ment, which  our  faculties  and  nature  seem  ca- 
pable of,  the  seeing  and  comprehending  the 
whole  plan  of  the  Creator,  in  forming  the  uni- 
verse and  in  directing  all  its  operations  ? 

But  the  more  immediate  purposes  of  anato- 
my concern  those  who  are  to  be  the  guardians 
of  health,  as  this  study  is  necessary  to  lay  a 
foundation  for  all  the  branches  of  medicine. 
The  more  we  know  of  our  fabric,  the  more 
reason  we  have  to  believe,  that  if  our  senses 
were  more  acute,  and  our  judgment  more  en- 
larged, we  should  be  able  to  trace  many 
springs  of  life  which  are  now  hidden  from  us: 
by  the  same  sagacity  we  should  discover  the 
true  causes  and  nature  of  diseases  ; and  there- 
by be  enabled  to  restore  the  health  of  many, 
who  are  now,  from  our  more  confined  know- 
ledge, said  to  labour  under  incurable  disor- 
ders. By  such  an  intimate  acquaintance  with 
the  ceconomy  of  our  bodies,  we  should  disco- 
ver even  the  seeds  of  diseases,  and  destroy 
them  before  they  had  taken  root  in  the  consti- 
tution. 

That  anatomy  is  the  very  basis  of  surgery 
every  body  allows.  It  is  dissection  alone  that 
can  teach  us,  where  we  may  cut  the  living 
body  with  freedom  and  dispatch  ; and  where 
we  may  venture  with  great  circumspection  and 


44  Introduction  to  Anatomy. 

delicacy ; and  where  we  must  not,  upon  any 
account,  attempt  it.  This  informs  the  head, 
gives  dexterity  to  the  hand,  and  familiarizes 
the  heart  with  a sort  of  necessary  inhumanity, 
the  use  of  cutting-instruments  upon  our  fel- 
low-creatures. 

Besides  the  knowledge  of  our  body,  through 
all  the  variety  of  its  structure  and  operations  in 
a sound  state,  it  is  by  anatomy  only  that  we 
can  arrive  at  the  knowledge  of  the  true  nature 
of  most  of  the  diseases  which  afflict  humanity. 
The  symptoms  of  many  disorders  are  often 
equivocal ; and  diseases  themselves  are  thence 
frequently  mistaken,  even  by  sensible,  expe- 
rienced, and  attentive  physicians.  But  by  ana- 
tomical examination  after  death,  we  can  with 
certainty  find  out  the  mistake,  and  learn  to 
avoid  it  in  any  similar  case. 

This  use  of  anatomy  has  been  so  generally 
adopted  by  the  moderns,  that  the  cases  alrea- 
dy published  are  almost  innumerable  : Man- 
getus,  Morgagni,  indeed  many  of  the  best  mo- 
dern writings  in  physic,  are  full  of  them.  And 
if  we  look  among  the  physicians  of  the  best 
character,  and  observe  those  who  have  the 
art  itself,  rather  than  the  craft  of  the  profes- 
sion at  heart ; we  shall  find  them  constantly 
taking  pains  to  procure  leave  to  examine  the 
bodies  of  their  patients  after  death. 

After  having  considered  the  rise  and  pro- 
gress of  anatomy ; the  various  discoveries 
that  have  been  made  in  it,  from  time  to  time  ; 
the  great  number  of  diligent  observers  who 
have  applied  themselves  to  this  art ; and  the 


Introduction  to  Anatomy.  45 

importance  of  the  study,  not  only  for  the  pre- 
vention and  cure  of  diseases,  but  in  furnish- 
ing the  liveliest  proofs  of  divine  wisdom;  the 
following  questions  seem  naturally  to  arise: 
For  what  purpose  is  there  such  a variety  of 
parts  in  the  human  body  ? Why  such  a com- 
plication of  nice  and  tender  machinery  ? Why 
was  there  not  rather  a more  simple,  less  deli- 
cate, and  less  expensive  frame  ?* 

In  order  to  acquire  a satisfactory  general 
idea  of  this  subject,  and  find  a solution  of  all 
such  questions,  let  us,  in  our  imaginations, 
make  a man : in  other  words  let  us  suppose 
that  the  mind , or  immaterial  part,  is  to  be 
placed  in  a corporeal  fabric,  in  order  to  hold 
a correspondence  with  other  material  beings 
by  the  intervention  of  the  body ; and  then 
consider,  a priori , what  will  be  wanted  for  her 
accommodation.  In  this  inquiry,  we  shall 
plainly  see  the  necessity  or  advantage,  and 
therefore  the  final  cause,  of  most  of  the  parts 
which  we  actually  find  in  the  human  body. 
And  if  we  consider  that,  in  order  to  answer 
some  of  the  requisites,  human  wit  and  inven- 
tion would  be  very  insufficient ; we  need  not 
be  surprised  if  we  meet  with  some  parts  of 
the  body  whose  use  we  cannot  yet  perceive,  and 
with  some  operations  and  functions  which  we 
cannot  explain.  We  can  see  that  the  whole 
bears  the  most  striking  characters  of  excelling 
wisdom  and  ingenuity : but  the  imperfect  sen- 


* The  following  beautiful  representation  is  taken  from  the  late 
Dr.  Hunter’s  Introductory  Lecture  in  Anatomy. 


46  Introduction  to  Anatomy. 

ses  and  capacity  of  man  cannot  pretend  to 
reach  every  part  of  a machine,  which  nothing 
less  than  the  intelligence  and  power  of  the 
Supreme  Being  could  contrive  and  execute. 

First,  then,  the  mind,  the  thinking,  imma- 
terial agent,  must  be  provided  with  a place  of 
immediate  residence,  which  shall  have  all  the 
requisites  for  the  union  of  spirit  and  body  \ 
accordingly  she  is  provided  with  the  brain , 
where  she  dwells  as  governor  and  superintend- 
ant  of  the  whole  fabric. 

In  the  next  place,  as  she  is  to  hold  a corre- 
spondence with  all  the  material  beings  around 
her,  she  must  be  supplied  with  organs  fitted 
to  receive  the  different  kinds  of  impressions 
which  they  will  make.  In  fact,  therefore,  we 
see  that  she  is  provided  with  the  organs  of 
sense,  as  we  call  them  : the  eye  is  adapted  to 
light ; the  ear  to  sound ; the  nose  to  smell ; 
the  mouth  to  taste ; and  the  skin  to  touch. 

Further : She  must  be  furnished  with  or- 
gans of  communication  between  herself  in  the 
brain  and  those  organs  of  sense,  to  give  her 
information  of  all  the  impressions  that  are 
made  upon  them : and  she  must  have  organs 
between  herself  in  the  brain  and  every  other 
part  of  the  body,  fitted  to  convey  her  com- 
mands and  influence  over  the  whole.  For 
these  purposes  the  nerves  are  actually  given. 
They  are  chords,  which  rise  from  the  brain, 
the  immediate  residence  of  the  mind,  and  dis- 
perse themselves  in  branches  through  all  parts 
of  the  body.  They  convey  ail  the  different 
kinds  of  sensations  to  the  mind,  in  the  brain ; 


Introduction  to  Anatomy. 


47 


and  likewise  carry  out  from  thence  all  her  com- 
mands or  influence  to  the  other  parts  of  the 
body.  They  are  intended  to  be  occasional  mo- 
nitors against  all  such  impressions  as  might  en- 
danger the  well-being  of  the  whole,  or  of  any 
particular  part ; which  vindicates  the  Creator 
of  all  things,  in  having  actually  subjected  us 
to  those  many  disagreeable  and  painful  sensa- 
tions which  we  are  exposed  to  from  a thousand 
accidents  in  life. 

Moreover,  the  mind,  in  this  corporeal  sys- 
tem, must  be  endued  with  the  power  of  mov- 
ing from  place  to  place,  that  she  may  have  in- 
tercourse with  a variety  of  objects  ; that  she 
may  fly  from  such  as  are  disagreeable,  danger- 
ous or  hurtful,  and  pursue  such  as  are  plea- 
sant or  useful  to  her.  And  accordingly  she  is 
furnished  with  limbs,  and  with  muscles  and 
tendons,  the  instruments  of  motion,  which  are 
found  in  every  part  of  the  fabric  where  motion 
is  necessary. 

But  to  support,  to  give  firmness  and  shape 
to  the  fabric  ; to  keep  the  softer  parts  in  their 
proper  places  ; to  give  fixed  points  for,  and  the 
proper  direction  to  its  motions,  as  well  as  to 
protect  some  of  the  more  important  and  tender 
organs  from  external  injuries ; there  must  be 
some  firm  prop-work  interwoven  through  the 
whole.  And,  in  fact,  for  such  purposes  the 
bones  are  given. 

The  prop-work  must  not  be  made  into  one 
rigid  fabric,  for  that  would  prevent  motion. 
Therefore  there  are  a number  of  bones. 


48  Introduction  to  Anatomy. 

These  pieces  must  all  be  firmly  bound  toge- 
ther, to  prevent  their  dislocation.  And  this 
end  is  perfectly  well  answered  by  the  liga- 
ments. 

The  extremities  of  these  bony  pieces,  where 
they  move  and  rub  upon  one  another,  must 
have  smooth  and  slippery  surfaces  for  easy 
motion.  This  is  most  happily  provided  for, 
by  the  cartilages  and  mucus  of  the  joints. 

The  interstices  of  all  those  parts  must  be 
filled  up  with  some  soft  and  ductile  matter, 
which  shall  keep  them  in  their  places,  unite 
them,  and  at  the  same  time  allow  them  to  move 
a little  upon  one  another.  And  these  purposes 
are  answered  by  the  cellular  membrane  or  adi- 
pose substance. 

There  must  be  an  outward  covering  over 
the  whole  apparatus,  both  to  give  it  compact- 
ness and  to  defend  it  from  a thousand  injuries  : 
which,  in  fact,  are  the  very  purposes  of  the 
skin  and  other  integuments. 

Lastly,  the  mind  being  formed  for  society 
and  intercourse  with  beings  of  her  own  kind, 
she  must  be  endued  with  powers  of  expressing 
and  communicating  her  thoughts  by  some  sen- 
sible marks  or  signs  ; which  shall  be  both  easy 
to  herself,  and  admit  of  great  variety ; and  ac- 
cordingly she  is  provided  with  the  organs  and 
faculty  of  speech,  by  which  she  can  throw  out 
signs  with  amazing  facility,  and  vary  them  with- 
out end. 

Thus  we  have  built  up  an  animal  body  which 
would  seem  to  be  pretty  complete  : but  as  it 
is  the  nature  of  matter  to  be  altered  and  work- 


Introduction  to  Anatomy.  49 

ed  upon  by  matter ; so  in  a very  little  time  such 
a living  creature  must  be  destroyed,  if  there  is 
no  provision  for  repairing  the  injuries  which 
she  must  commit  upon  herself,  and  those  which 
she  must  be  exposed  to  from  without.  There- 
fore a treasure  of  blood  is  actually  provided  in 
the  heart  and  vascular  system,  full  of  nutritious 
and  healing  particles,  fluid  enough  to  penetrate 
into  the  minutest  parts  of  the  animal ; impelled 
by  the  heart,  and  conveyed  by  the  arteries,  it 
washes  every  part,  builds  up  what  was  broken 
down,  and  sweeps  away  the  old  and  useless 
materials.  Hence  we  see  the  necessity  or  ad- 
vantage of  the  heart  and  arterial  system. 

What  more  there  was  of  this  blood  than 
enough  to  repair  the  present  damages  of  the 
machine,  must  not  be  lost,  but  should  be  re- 
turned again  to  the  heart ; and  for  this  purpose 
the  venous  system  is  actually  provided.  These 
requisites  in  the  animal  explain,  a priori,  the 
circulation  of  the  blood. 

The  old  materials  which  were  become  use- 
less, and  are  swept  off  by  the  current  of  blood, 
must  be  separated  and  thrown  out  of  the  sys- 
tem. Therefore  glands,  the  organs  of  Secre- 
tion, are  given  for  straining  whatever  is  redun- 
dant, vapid,  or  noxious,  from  the  mass  of 
blood ; and  when  strained,  they  are  thrown 
out  by  emunctories,  called  organs  of  Excre- 
tion. 

But  now,  as  the  machine  must  be  constant- 
ly wearing,  the  reparation  must  be  carried  on 
without  intermission,  and  the  strainers  must 
always  be  emoloyed.  Therefore  there  is  ac- 

G 


50  Introduction  to  Anatomy. 

tually  a perpetual  circulation  of  the  blood,  and 
the  secretions  are  always  going  on. 

Even  all  this  provision,  however,  would  not 
be  sufficient ; for  that  store  of  blood  would 
soon  be  consumed,  and  the  fabric  would  break 
down,  if  there  were  not  a provision  made  for 
fresh  supplies.  These  we  observe,  in  fact,  are 
profusely  scattered  round  her  in  the  animal 
and  vegetable  kingdoms : and  she  is  furnished 
with  hands,  the  fittest  instruments  that  could 
have  been  contrived,  for  gathering  them,  and 
for  preparing  them  in  a variety  of  ways  for  the 
mouth. 

But  these  supplies,  which  we  call  food, 
must  be  considerably  changed  ; they  must  be 
converted  into  blood.  Therefore  she  is  pro- 
vided with  teeth  for  cutting  and  bruising  the 
food,  and  with  a stomach  for  melting  it  down  : 
In  short,  with  all  the  organs  subservient  to  di- 
gestion.— The  finer  parts  of  the  aliments  only 
can  be  useful  in  the  constitution : these  must 
be  taken  up  and  conveyed  into  the  blood,  and 
the  dregs  must  be  thrown  off.  With  this  view 
the  intestinal  canal  is  actually  given.  It  sepa- 
rates the  nutritious  part,  which  we  call  chyle , 
to  be  conveyed  into  the  blood  by  the  system 
of  absorbent  vessels  ; and  the  faces  pass  down- 
wards, to  be  conducted  out  of  the  body. 

Now  we  have  got  our  animal  not  only  fur- 
nished with  what  is  wanted  for  its  immediate 
existence,  but  also  with  the  powers  of  protract- 
ing that  existence  to  an  indefinite  length  of 
time.  But  its  duration,  we  may  presume,  must 
necessarily  be  limited : for  as  it  is  nourished, 


Introduction  to  Anatomy.  51 

grows,  and  is  raised  up  to  its  full  strength  and 
utmost  perfection  ; so  it  must,  in  time,  in  com- 
mon with  all  material  beings,  begin  to  decay, 
and  then  hurry  on  to  final  ruin.  Hence  we 
see  the  necessity  of  a scheme  for  renovation. 
Accordingly  wise  Providence,  to  perpetuate, 
as  welPas  preserve  his  work,  besides  giving  a 
strong  appetite  for  life  and  self-preservation, 
has  made  animals  male  and  female,  and  given 
them  such  organs  and  passions  as  will  secure 
the  propagation  of  the  species  to  the  end  of 
time. 

Thus  we  see,  that  by  the  very  imperfect 
survey  which  human  reason  is  able  to  take  of 
this  subject,  the  animal  man  must  necessarily 
be  complex  in  his  corporeal  system,  and  in  its 
operations. 

He  must  have-one  great  and  general  system, 
the  vascular,  branching  through  the  whole  for 
circulation : Another  the  nervous,  with  its  ap- 
pendages the  organs  of  sense,  for  every  kind 
of  feeling  : And  a third,  for  the  union  and 
connection  of  all  those  parts. 

Besides  these  primary  and  general  systems, 
he  requires  others  which  may  be  more  local, 
or  confined:  One  for  strength,  support,  and 
protection ; the  bony  compages  : Another  for 
the  requisite  motions  of  the  parts  among  them- 
selves, as  well  as  for  moving  from  place  to 
place  ; the  muscular  part  of  the  body : Ano- 
ther to  prepare  nourishment  for  the  daily  re- 
cruit of  the  body ; the  digestive  organs  : And 
one  for  propagating  the  species ; the  organs  of 
generation. 


52  Introduction  to  Anatomy. 

And  in  taking  this  general  survey  of  what 
would  appear,  a priori , to  be  necessary  for 
adapting  an  animal  to  the  situations  of  life,  we 
observe  with  great  satisfaction,  that  man  is 
accordingly  made  of  such  systems,  and  for 
such  purposes.  Fie  has  them  all ; and  he  has 
nothing  more,  except  the  organs  of  respira- 
tion. Breaming  it  seemed  difficult  to  account 
for  a priori:  we  only  knew  it  to  be  in  fact 
essentially  necessary  to  life.  Notwithstanding 
this,  when  wre  saw  all  the  other  parts  of  the  bo- 
dy, and  their  functions,  so  well  accounted  for, 
and  so  wisely  adapted  to  their  several  purpo- 
ses, there  could  be  no  doubt  that  respiration 
was  so  likewise  : And  accordingly,  the  disco- 
veries of  Dr.  Priestley  have  lately  thrown 
light  upon  this  function  also,  as  will  be  shown 
in  its  proper  place. 

Of  all  the  different  systems  in  the  human 
body,  the  use  and  necessity  are  not  more  ap- 
parent, than  the  wisdom  and  contrivance  which 
has  been  exerted  in  putting  them  all  into  the 
most  compact  and  convenient  form  : indispos- 
ing them  so,  that  they  shall  mutually  receive, 
and  give  helps  to  one  another ; and  that  all,  or 
many  of  the  parts,  shall  not  only  answer  their 
principal  end  or  purpose,  but  operate  success- 
fully and  usefully  in  a variety  of  secondary 
ways. 

If  we  consider  the  whole  animal  machine 
in  this  light,  and  compare  it  with  any  machine 
in  which  human  art  has  exerted  its  utmost; 
suppose  the  best  constructed  ship  that  ever 
was  built,  we  shall  be  convinced  beyond  the 


Introduction  to  Anatolmy . S3 

possibility  of  doubt,  that  there  are  intelligence 
and  power  far  surpassing  what  humanity  can 
boast  of. 

One  superiority  in  the  natural  machine  is 
peculiarly  striking.- — In  machines  of  human 
contrivance  or  art,  there  is  no  internal  power, 
no  principle  in  the  machine  itself,  by  which  it 
can  alter  and  accommodate  itself  to  any  injury 
which  it  may  suffer,  or  make  up  any  injury 
which  admits  of  repair.  But  in  the  natural 
machine,  the  animal  body,  this  is  most  won- 
derfully provided  for,  by  internal  powers  in 
the  machine  itself ; many  of  which  are  not 
more  certain  and  obvious  in  their  effects,  than 
they  are  above  all  human  comprehension  as  to 
the  manner  and  means  of  their  operation. 
Thus,  a wound  heals  up  of  itself ; a broken 
bone  is  made  firm  again  by  a callus  ; a dead 
part  is  separated  and  thrown  off ; noxious  juic- 
es are  driven  out  by  some  of  the  emunctories; 
a redundancy  is  removed  by  some  spontane- 
ous bleeding  ; a bleeding  naturally  stops  of  it- 
self ; and  a great  loss  of  blood,  from  any  cause, 
is  in  some  measure  compensated,  by  a con- 
tracting power  in  the  vascular  system,  which 
accommodates  the  capacity  of  the  vessels  to 
the  quantity  contained.  The  stomach  gives 
information  when  the  supplies  have  been  ex- 
pended ; represents,  with  great  exactness,  the 
quantity  and  the  quality  of  what  is  wanted  in 
the  present  state  of  the  machine  ; and  in  pro- 
portion as  she  meets  with  neglect,  rises  in  her 
demand,  urges  her  petition  in  a louder  tone, 
and  with  more  forcible  arguments.  For  its 


54  Introduction  to  Anatomy . 

protection,  an  animal  body  resists  heat  and 
cold  in  a very  wonderful  manner,  and  pre- 
serves an  equal  temperature  in  a burning  and 
in  a freezing  atmosphere. 

A farther  excellence  or  superiority  in  the 
natural  machine,  if  possible,  still  more  aston- 
ishing, more  beyond  all  human  comprehen- 
sion, than  what  we  have  been  speaking  of,  is 
the  following.  Besides  those  internal  powers 
of  self-preservation  in  each  individual,  when 
two  of  them  co-operate,  or  act  in  concert,  they 
are  endued  with  powers  of  making  other  ani- 
mals or  machines  like  themselves,  which  again 
are  possessed  of  the  same  powers  of  produc- 
ing others,  and  so  of  multiplying  the  species 
without  end. 

These  are  powers  which  mock  all  human  in- 
vention or  imitation.  They  are  characterise 
tics  of  the  divine  Architect. 

Having  premised  this  general  account  of  the 
subject,  we  shall  next  consider  the  method  to 
be  observed  in  treating  it. 

The  study  of  the  human  body,  as  already 
noticed,  is  commonly  divided  into  two  parts. 
The  first,  which  is  called  Anatomy , relates  to 
the  matter  and  structure  of  its  parts  ; the  se- 
cond, called  Physiology  and  Animal  ceconomy , 
relates  to  the  principles  and  laws  of  its  inter- 
nal operations  and  functions. 

As  the  body  is  a compound  of  solids  and 
fluids,  Anatomy  is  divided  into, 

1.  The  Anatomy  of  the  solids,  and 

2.  The  Anatomy  of  the  fluids. 


Introduction  to  Anatomy.  55 

I.  The  Solids,  by  which  we  mean  all  parts 
of  our  body,  which  are  not  fluid,  are  general- 
ly divided  into  two  classes,  viz. 

1.  The  hard  solids  or  bones.  This  part  of 
anatomy  is  called  Osteology ; which  signifies 
the  doctrine  of  the  bones. 

2.  The  softer  solids ; which  part  is  called 
Sarcology,  viz.  the  doctrine  of  flesh. 

This  division  of  the  solids,  we  may  observe, 
has  probably  taken  its  origin  from  the  vulgar 
observation,  that  the  body  is  made  of  bone 
and  flesh.  And  as  there  are  many  different 
kinds  of  what  are  called  soft  or  fleshy  parts, 
Sarcology  is  subdivided  into, 

(l.)  Angeiology , or  the  doctrine  of  vessels; 
by  which  is  commonly  understood  bloocl-vessels : 
(2.)  Adenology , of  glands: 

(3.)  Neurology , of  nerves: 

(4.)  Myology , of  muscles  : and, 

(5.)  Splanchnology , of  the  viscera  or  bow- 
els. There  is,  besides,  that  part  which  treats 
of  the  organs  of  sense  and  of  the  integuments. 

This  division  of  the  solids  has  been  here 
mentioned,  rather  for  the  sake  of  explaining 
so  many  words,  which  are  constantly  used 
by  anatomists,  than  for  its  importance  or  ac- 
curacy. For  besides  many  other  objections 
that  might  be  urged,  there  are  in  the  body 
three  species  of  solids,  viz.  gristle  or  carti- 
lage, hair,  and  nails  ; which  are  of  an  inter- 
mediate nature  between  bone  and  flesh ; and 
therefore  cannot  so  properly  be  brought  into 
the  osteology  or  the  sarcology.  The  cartila- 
ges were  classed  with  the  bones  ; because  the 


56  Introduction  to  Anatomy . 

greatest  number  of  them  are  appendages  to 
bones  : and  for  the  like  reason  the  hair  and  the 
nails  were  classed  with  the  integuments. 

II.  The  Fluids  of  the  human  body  may  be 
divided  into  three  kinds,  which  Dr.  Hunter 
calls  the  crude , the  general  or  perfect , and  the 
local  or  secreted  fluid. 

1.  By  the  crude  fluid  is  meant  the  chyle,  and 
whatever  is  absorbed  at  the  surfaces  of  the 
body  ; in  other  words,  what  is  recently  taken 
into  the  body,  and  is  not  yet  mixed  with  or 
converted  into  blood. 

2.  The  general  or  perfect  fluid  is  the  blood 
itself ; to  wit,  what  is  contained  in  the  heart, 
arteries,  and  veins,  and  is  going  on  in  the 
round  of  the  circulation. 

3.  The  local  or  secreted , are  those  fluids  pe- 
culiar to  particular  parts  of  the  body,  which 
are  strained  off  from  the  blood,  and  yet  are 
very  different  in  their  properties  from  the  blood. 
They  are  commonly  called  secretions ; and 
some  are  useful,  others  excrementitious. 

In  treating  of  the  Physiology , it  is  very  dif- 
ficult to  say  what  plan  should  be  followed  ; 
for  every  method  which  has  been  yet  proposed, 
is  attended  with  manifest  inconvenience.  The 
powers  and  operations  of  the  machine  have 
such  a dependence  upon  one  another,  such 
connections  and  reciprocal  influence,  that  they 
cannot  well  be  understood  or  explained  sepa- 
rately. In  this  sense  our  body  may  be  com- 
pared to  a circular  chain  of  powers,  in  which 
nothing  is  first  or  last,  nothing  solitary  or  in- 
dependent ; so  that  wherever  we  begin,  we 


Osteology . 


57 


find  that  there  is  something  preceding  which 
we  ought  to  have  known.  If  we  begin  with 
the  brain  and  the  nerves,  for  example,  we 
shall  find  that  these  cannot  exist,  even  in  idea, 
without  the  heart:  if  we  set  out  with  the  heart 
and  vascular  system,  we  shall  presently  be 
sensible,  that  the  brain  and  nerves  must  be 
supposed:  or,  should  we  take  up  the  mouth, 
and  follow  the  course  of  the  aliment,  we  should 
see  that  the  very  first  organ  which  presents 
itself,  supposed  the  existence  of  both  the  heart 
and  brain : Wherefore  we  shall  incorporate  the 
Physiology  with  the  Anatomy,  by  attempting 
to  explain  the  functions  after  we  have  demon- 
strated the  organs. 


Part  I.  OSTEOLOGY. 

WE  begin  with  the  bones,  which  may  be 
considered  as  the  great  support  of  the 
body,  tending  to  give  it  shape  and  firmness. — 
But  before  we  enter  into  the  detail  of  each  par- 
ticular bone,  it  will  be  necessary  to  describe 
their  composition  and  connections,  and  to  ex- 
plain the  nature  of  the  different  parts  which 
have  an  immediate  relation  to  them  ; as  the  car- 
tilages, ligaments,  periosteum,  marrow,  and 
synovial  glands. 


H 


58 


Osteology* 


Sect.  I.  Of  the  Bones  in  general , with  their 
Appendages , &c* 

The  bones  are  of  a firm,  and  hard*  sub- 
stance, of  a white  colour,  and  perfectly  insen- 
sible. They  are  the  most  compact  and  solid 
parts  of  the  body,  and  serve  for  the  attachment 
and  support  of  all  the  other  parts. 

Three  different  substances  are  usually  dis- 
tinguished in  them;  their  exterior  or  bony 
part,  properly  so  called;  their  spongy  cells; 
and  their  reticular  substance.  The  first  of  these 
is  formed  of  many  laminae  or  plates,  compos- 
ing a firm  hard  substance  — The  spongy  or 
cellular  part  is  so  called  on  account  of  its  re- 
semblance to  a sponge,  from  the  little  cells 
which  compose  it.  This  substance  forms  al- 
most the  whole  of  the  extremities  of  cylindrical 
bones.  The  reticular  part  is  composed  of  fi- 
bres, which  cross  each  other  in  different  direc- 
tions. This  net-work  forms  the  internal  sur- 
face of  those  bones  which  have  cavities. 

The  flat  bones,  as  those  of  the  head,  are 
composed  only  of  the  laminae  and  the  cellular 
substance.  This  last  is  usually  found  in  the 
middle  of  the  bone  dividing  it  into  two  plates, 
and  is  there  called  diploe . 

* Mr.  Scheele  lias  litely  difcovered  that  bones  contain  the 
phofphoric  acid  urited  with  calcareous  earth;  and  that  to  this 
combination  they  owe  their  firmnefs. 


Osteology. 


59 


Gagliardi,  who  pretended  to  have  discover- 
ed an  infinite  number  of  claviculi*  or  bony 
processes,  which  he  describes  as  traversing 
the  laminae  to  unite  them  together,  has  endea- 
voured to  support  this  pretended  discovery  by 
the  analogy  of  bones  to  the  bark  of  trees,  in 
which  certain  woody  nails  have  been  remark- 
ed ; but  this  opinion  seems  to  be  altogether 
fanciful. 

Some  writers  have  supposed,  that  the 
bones  are  formed  by  layers  of  the  perioste- 
um, which  gradually  ossify,  in  the  same  man- 
ner as  the  timber  is  formed  in  trees  by  the 
hardening  of  the  white  substance  that  is  found 
between  the  inner  bark  and  the  wood.  M. 
Duhamel,  who  has  adopted  this  opinion,  fed 
different  animals  with  madder  and  their  ordi- 
nary food  alternately  during  a certain  time ; 
and  he  asserts,  that  in  dissecting  their  bones, 
he  constantly  observed  distinct  layers  of  red 
and  white,  which  corresponded  with  the  length 
of  time  they  had  lived  on  madder  or  their 
usual  aliment.  But  it  has  since  been  proved 
by  Detleff,  that  M.  Duhamel’s  experiments 
were  inaccurate,  and  that  neither  the  perios- 
teum nor  the  cartilages  are  tinged  by  the  use 
of  madder,  which  is  known  to  affect  the  bones 
only. 

We  usually  consider  in  a bone,  its  body 
and  its  extremities.  The  ancients  gave  the 

* In  his  Anat.  OJJium  nov.  invent,  illujlrat.  he  defcribes  four 
kinds  of  thefe  claviculi  or  nails,  viz.  the  perpendicular,  oblique* 
headed,  and  crooked. 


60 


Osteology. 


name  of  diaphysis  to  the  body  or  middle  part, 
and  divided  the  extremities  into  apophysis  and 
epiphysis.  An  apophysis,  or  process,  as  it 
is  more  commonly  called,  is  an  eminence  con- 
tinued from  the  body  of  the  bone,  whereas  an 
epiphysis  is  at  first  a sort  of  appendage  to  the 
bone,  by  means  of  an  intermediate  cartilage. 
Many  epiphyses,  which  appear  as  distinct 
bones  in  the  foetus,  afterwards  become  apophy- 
ses ; for  they  are  at  length  so  completely  unit- 
ed to  the  body  of  the  bone  as  not  to  be  distin- 
guishable from  it  in  the  adult  state.  It  is  not 
unusual,  however,  at  the  age  of  18  and  even 
20  years,  to  find  the  extremities  of  bones  still 
in  the  state  of  epiphysis. 

The  names  given  to  the  processes  of  bones 
are  expressive  of  their  shape,  size,  or  use ; 
thus  if  a process  is  large  and  of  a spherical 
form,  it  is  called  caput , or  head ; if  the  head 
is  flatted,  it  is  termed  condyle.  Some  proces- 
ses, from  their  resemblance  to  a stiletto,  a 
breast,  or  the  beak  of  a crow,  are  called  styloid , 
mastoid , or  coracoid : others  are  styled  ridges 
or  spines.  The  two  processes  of  the  os  femo- 
ris  derive  their  name  of  trochanters  from  their 
use. 

A bone  has  its  cavities  as  well  as  processes. 
These  cavities  either  extend  quite  through  its 
substance,  or  appear  only  as  depressions.  The 
former  are  called  foramina  or  holes , and  these 
foramina  are  sometimes  termed  canals  or  con- 
duits, according  to  their  form  and  extent.  Of 
the  depressions,  some  are  useful  in  articuda- 
tion.  These  are  called  cotyloid  when  they  are 


Osteology. 


61 


deep,  as  is  the  case  with  the  os  innominatum, 
where  it  receives  the  head  of  the  os  femoris ; 
or  glenoid  when  they  are  superficial,  as  in  the 
scapula,  where  it  receives  the  os  humeri.  Of 
the  depressions  that  are  not  designed  for  arti- 
culation, those  which  have  small  apertures  are 
called  sinuses ; others  that  are  large,  and  not 
equally  surrounded  by  high  brims,  are  styled 
fossa  ; such  as  are  long  and  narrow,  furrows  ; 
or  if  broad  and  superficial  without  brims,  si- 
nuosities. Some  are  called  digital  impressions , 
from  their  resemblance  to  the  traces  of  a fin- 
ger on  soft  bodies. 

We  shall  abridge  this  article,  which  is  ex- 
ceedingly diffuse  in  the  generality  of  anatomi- 
cal books,  and  will  endeavour  to  describe  it 
with  all  the  clearness  it  will  allow. 

The  bones  composing  the  skeleton  are  so 
constructed,  that  the  end  of  every  bone  is  per- 
fectly adapted  to  the  extremity  of  that  with 
which  it  is  connected,  and  this  connection 
forms  what  is  called  their  articulation. 

Articulation  is  divided  into  diartlirosis , sy- 
nartlirosis , and  amphiarthrosis , or  moveable, 
immovable,  and  mixed  articulation.  Each  of 
the  two  first  has  its  subdivisions.  Thus  the 
Diarthrosis , or  moveable  articulation,  includes, 
1.  The  enarthrosis,  as  it  is  called,  when  a 
large  head  is  admitted  into  a deep  cavity,  as 
in  the  articulation  of  the  os  femoris  with  the 
os  innominatum.  2.  Arthrodia,  when  a round 
head  is  articulated  with  a superficial  cavity,  as 
is  the  case  of  the  os  humeri  and  scapula.  3. 
Ginglimus,  or  hinge-like  articulation,  as  in  the 


62 


Osteology. 


connection  of  the  thigh-bone  with  the  tibia. 
The  enarthrosis  and  arthrodia  allow  of  motion 
to  all  sides  ; the  ginglimus  only  of  flection  and 
extension. 

The  syjiarthrosis , or  immoveable  articula- 
tion, includes,  1.  The  suture,  when  the  two 
bones  are  indented  into  each  other,  as  is  the 
case  with  the  parietal  bones.  2.  Gomphosis, 
when  one  bone  is  fixed  into  another,  in  the 
manner  the  teeth  are  placed  in  their  sockets. 

The  term  amphiarthrosis  is  applied  to  those 
articulations  which  partake  both  of  the  synar- 
throsis and  diarthrosis,  as  is  the  case  with  the 
bones  of  the  vertebrae,  which  are  capable  of 
motion  in  a certain  degree,  although  they  are 
firmly  connected  together  by  intermediate  car- 
tilages. 

What  is  called  symphysis  is  the  union  of 
two  bones  into  one ; as  in  the  lower  jaw,  for 
instance,  which  in  the  foetus  consists  of  two 
distinct  bones,  but  becomes  one  in  a more  ad- 
vanced age,  by  the  ossification  of  the  uniting 
cartilage. 

When  bones  are  thus  joined  by  the  means 
of  cartilages,  the  union  is  styled  synchondro- 
sis ; when  by  ligaments,  syneurosis. 

Cartilages  are  white,  solid,  smooth,  and 
elastic  substances,  between  the  hardness  of 
bones  and  ligaments,  and  seemingly  of  a fi- 
brous texture.  We  are  not  able  to  trace  any 
vessels  into  their  substance  by  injection,  nor 
are  they  ever  found  tinged  in  animals  that  have 
been  fed  with  madder. 


Osteology . 


63 


They  may  be  distinguished  into,  1st,  Those 
which  are  connected  with  the  bones ; and, 
2dly,  Those  which  belong  to  other  parts  of 
the  body.  The  first  serve  either  to  cover  the 
ends  and  cavities  of  bones  intended  for  mo- 
tion, as  in  the  articulations,  where  by  their 
smoothness  they  facilitate  motions,  which  the 
bones  alone  could  not  execute  with  so  much 
freedom ; or  they  serve  to  unite  bones  toge- 
ther, as  in  the  symphysis  pubis,  or  to  length- 
en them,  as  in  the  ribs. 

Many  of  them  ossifying  as  we  advance  in 
life,  their  number  is  less  in  the  adult  than  in 
the  foetus,  and  of  course  there  are  fewer  bones 
in  the  old  than  in  the  young  subject. 

Of  the  second  class  of  cartilages,  or  those 
belonging  to  the  soft  parts,  we  have  instances 
in  the  larynx,  where  we  find  them  useful  in 
the  formation  of  the  voice,  and  for  the  attach- 
ment of  muscles. 

The  periosteum  is  a fine  membrane  of  a 
compact  cellular  texture,  reflected  from  one 
joint  to  another,  and  serving  as  a common 
covering  to  the  bones.  It  has  sanguiferous 
and  lymphatic  vessels,  and  is  supplied  with 
nerves  from  the  neighbouring  parts.  It  ad- 
heres very  firmly  to  their  surface,  and  by  its 
smoothness  facilitates  the  motion  of  muscles. 
It  likewise  supports  the  vessels  that  go  to  be 
distributed  through  the  substance  of  the  bones, 
and  may  serve  to  strengthen  the  articulations. 
At  the  extremities  of  bones,  where  it  is  found 
covering  a cartilage,  it  has  by  some  been  im- 
properly considered  as  a distinct  membrane, 


64 


Osteology. 


and  named  perichondrium.  This,  in  its  use 
and  structure,  resembles  the  periosteum. 
Where  it  covers  the  bones  of  the  skull,  it 
has  gotten  the  name  of  pericranium > 

The  periosteum  is  not  a production  of  the 
dura  mater,  as  the  ancients,  and  after  them 
Havers,  imagined ; nor  are  the  bones  formed 
by  the  ossification  of  this  membrane,  at  least 
when  it  is  in  a sound  state,  as  some  late  wri- 
ters have  supposed. 

The  periosteum  is  deficient  in  the  teeth 
above  the  sockets,  and  in  those  parts  of  bones 
to  which  ligaments  or  tendons  are  attached. 

The  marrow  is  a fat  oily  substance,  filling 
the  cavities  of  bones.  In  the  great  cavities  of 
long  bones  it  is  of  a much  firmer  consistence 
than  in  the  cells  of  their  spongy  part.  In  the 
former  it  inclines  somewhat  to  a yellowish 
tinge,  and  is  of  the  consistence  of  fat ; in  the 
latter  it  is  more  fluid,  and  of  a red  colour. 
This  difference  in  colour  and  consistence  is 
owing  to  accidental  causes  ; both  kinds  are  of 
the  same  nature,  and  may  both  be  described 
under  the  common  name  of  marrow,  though 
some  writers  give  the  name  only  to  the  fat-like 
substance,  and  call  the  other  the  medullary 
juice. 

The  marrow  is  contained  in  a very  fine  and 
transparent  membrane,  which  is  supplied  with 
a great  number  of  blood-vessels,  chiefly  from 
the  periosteum.  This  membrana  medullaris 
adheres  to  the  inner  surface  of  the  bones, 
and  furnishes  an  infinite  number  of  minute 
bags  or  vesicles  for  inclosing  the  marrow, 


Osteology. 


65 


which  is  likewise  supported  in  the  cavities  of 
the  bones  by  the  long  filaments  of  their  reti- 
cular substance. 

Besides  the  vessels  from  the  periosteum, 
the  membrana  medullaris  is  furnished  with 
others,  which  in  the  long  bones  may  be  seen 
passing  in  near  the  extremities  of  the  bone, 
and  sending  off  numerous  branches  that  rami- 
fy through  all  the  vesicles  of  this  membrane. 

The  bones,  and  the  cells  containing  the 
marrow,  are  likewise  furnished  with  lympha- 
tics. By  their  means,  the  marrow,  like  the 
fat,  may  be  taken  up  in  a greater  quantity  than 
it  is  secreted ; and  hence  it  is  that  so  little  is 
found  in  the  bones  of  those  who  die  of  linger- 
ing diseases. 

It  is  still  a matter  of  controversy,  Whether 
the  marrow  is  sensible  or  not?  We  are  cer- 
tainly not  able  to  trace  any  nerves  to  it;  and 
from  this  circumstance,  and  its  analogy  to  fat, 
Haller  has  ventured  to  consider  it  as  insensi- 
ble. On  the  other  hand,  Duverney  asserts, 
that  an  injury  done  to  this  substance  in  a liv- 
ing animal  was  attended  with  great  pain.  In 
this  dispute  physiologists  do  not  seem  to  have 
sufficiently  discriminated  between  the  marrow 
itself  and  the  membranous  cells  in  which  it  is 
contained.  The  former,  like  the  fat,  being 
nothing  more  than  a secreted,  and  of  course 
an  inorganized,  matter,  may  with  propriety  be 
ranked  among  the  insensible  parts,  as  much  as 
inspissated  mucus  or  any  other  secreted  mat- 
ter in  the  body ; whereas  the  membrana  me- 
dullaris being  vascular,  though  it  possesses  but 

I 


66 


Osteology . 


an  obscure  degree  of  feeling  in  a sound  state, 
is  not  perfectly  insensible. 

The  marrow  was  formerly  supposed  to  be 
intended  for  the  nourishment  and  renewal  of 
the  bones ; but  this  doctrine  is  now  pretty  ge- 
nerally and  deservedly  exploded.  It  seems 
probable  that  the  marrow  is  to  the  bones  what 
fat  is  to  the  soft  parts.  They  both  serve  for 
some  important  purposes  in  the  animal  (econo- 
my ; but  their  particular  use  has  never  yet 
been  clearly  ascertained.  The  marrow,  from 
the  transudation  of  the  oil  through  the  bones 
of  a skeleton,  is  supposed  to  diminish  their 
brittleness;  and  Havers,  who  has  written  pro- 
fessedly on  the  bones,  describes  the  canals  by 
which  the  marrow  is  conveyed  through  every 
part  of  their  substance,  and  divides  them  into 
longitudinal  and  transverse  ones.  He  speaks 
of  the  first  as  extending  through  the  whole 
length  of  the  bone ; and  of  the  latter,  as  the 
passages  by  which  the  longitudinal  ones  com- 
municate with  each  other.  The  similarity  of 
these  to  the  large  cancelli  in  burnt  bones,  and 
the  transudation  of  the  oil  through  the  bones 
of  the  skeleton,  seems  to  prove  that  some  such 
passages  do  actually  exist. 

The  synovial  glands  are  small  bodies,*  sup- 
posed to  be  of  a glandular  structure,  and  ex- 
ceedingly vascular,  secreting  a fluid  of  a clear 
mucilaginous  nature,  which  serves  to  lubricate 
the  joints.  They  are  placed  in  small  cavities 

* It  is  now  much  doubted,  however,  whether  the  appear- 
ances in  the  joints,  which  are  usually  called  glands , art  any  thing 
more  than  assemblages  of  fat. 


Osteology. 


67 


in  the  articulations,  so  as  to  be  capable  of  be- 
ing gently  compressed  by  the  motion  of  the 
joint,  which  expresses  their  juice  in  propor- 
tion to  the  degree  of  friction.  When  the  sy- 
novia is  wanting,  or  is  of  too  thick  a consist- 
ence, the  joint  becomes  stiff  and  incapable  of 
flexion  or  extension.  This  is  what  is  termed 
anchilosis. 

Ligaments  are  white,  glistening,  inelastic 
bands,  of  a compact  substance,  more  or  less 
broad  or  thick,  and  serving  to  connect  the 
bones  together.  They  are  distinguished  by 
different  names  adapted  to  their  different  forms 
and  uses.  Those  of  the  joints  are  called  ei- 
ther round  or  bursal.  The  round  ligaments 
are  white,  tendinous,  and  inelastic.  They  are 
strong  and  flexible,  and  are  found  only  in  the 
joint  of  the  knee,  and  in  the  articulation  of  the 
os  femoris  with  the  os  innominatum.  The 
bursal,  or  capsular  ligaments,  surround  the 
whole  joint  like  a purse,  and  are  to  be  found 
in  the  articulations  which  allow  motion  every 
way,  as  in  the  articulation  of  the  arm  with  the 
scapula. 

Of  those  sacs  called  Burse?  mucosa , a few 
were  known  to  former  anatomists,  but  by  much 
the  greater  number  have  been  since  discover- 
ed by  Dr.  Monro,*  who  observes,  that  they 
are  to  be  met  with  in  the  extremities  of  the 
body  only;  that  many  of  them  are  placed  en- 
tirely on  the  inner  sides  of  the  tendons,  be- 
tween these  and  the  bones.  Many  others  co- 
ver not  only  the  inner,  but  the  outer  sides  of 

* See  Descripion  of  the  Bursa  Mucosa,  fee. 


68 


Osteology. 


the  tendons,  or  are  interposed  between  the  ten- 
dons and  external  parts,  as  well  as  between 
those  and  the  bones. 

Some  are  situated  between  the  tendons  and 
external  parts  only  or  chiefly,  some  between 
contiguous  tendons,  or  between  the  tendons 
or  the  ligaments  and  the  joints.  A few  such 
sacs  are  observed  where  the  processes  of  bones 
play  upon  the  ligaments,  or  where  one  bone 
plays  upon  another.  Where  two  or  more  ten- 
dons are  contiguous,  and  afterwards  separate 
from  each  other,  we  generally  find  a common 
bursa  divided  into  branches,  with  which  it 
communicates  ; and  a few  bursae  of  contigu- 
ous tendons  communicate  with  each  other. — 
Some  in  healthy  children,  communicate  with 
the  cavities  of  the  joints  ; and  in  many  old 
people  he  has  seen  such  communications  form- 
ed by  use  or  worn  by  friction,  independent  of 
disease. 

Their  proper  membrane  is  thin  and  trans- 
parent, but  very  dense,  and  capable  of  con- 
fining air  or  any  other  fluid.  It  is  joined  to  the 
neighbouringparts  by  the  common  cellular  sub- 
stance. Between  the  bursa  and  the  hard  sub- 
stance of  bone,  a thin  layer  of  cartilage  or 
of  tough  membrane  is  very  generally  interpos- 
ed. To  the  cellular  substance  on  the  outside 
of  the  bursa,  the  adipose  substance  is  con- 
nected; except  where  the  bursa  covers  a ten- 
don, cartilage,  or  bone,  much  exposed  to  pres- 
sure or  friction. 

In  several  places  a mass  of  fat,  covered 
with  the  continuation  of  the  membrane  of  the 


Osteology. 


69 


bursa,  projects  into  its  cavity.  The  edges 
of  this  are  divided  into  fringes. 

The  inner  side  of  the  membrane  is  smooth, 
and  is  extremely  slippery  from  the  liquor  se- 
creted in  it. 

The  structure  of  the  bursas  bears  a strong 
resemblance  to  the  capsular  ligaments  of  the 
joints.  1.  The  inner  layer  of  the  ligament, 
like  that  of  the  bursae,  is  thin  and  dense.  2, 
It  is  connected  to  the  external  ligaments  by 
the  common  cellular  substance.  3.  Between 
it  and  the  bones,  layers  of  cartilage,  or  the 
articular  cartilages,  are  interposed.  4.  At  the 
sides  of  the  joints,  where  it  is  not  subjected 
to  violent  pressure  and  friction,  the  adipose 
substance  is  connected  with  the  c.ellular  mem- 
brane. 5.  Within  the  cavities  of  the  joints 
we  observe  masses  of  fat  projecting,  covered 
with  similar  blood-vessels,  and  with  similar 
fimbriae  hanging  from  their  edges.  6.  In  the 
knee  the  upper  part  of  such  a mass  of  fat 
forms  what  has  been  called  the  mucilaginous 
gland  of  the  joint , and  the  under  part  projects 
into  the  bursa  behind  the  ligament  which  ties 
the  patella  to  the  tibia.  7.  The  liquor  which 
lubricates  the  bursae  has  the  same  colour,  con- 
sistence, and  properties  as  that  of  the  joints, 
and  both  are  affected  in  the  same  manner  bv 

J 

heat,  mineral  acids,  and  ardent  spirits.  8.  In 
some  places  the  bursas  constantly  communi- 
cate with  the  cavities  of  the  joints,  in  others 
they  generally  do  so  ; from  which  we  may  in- 
fer a sameness  of  structure. 

When  we  examine  the  fimbria!  common  to 
the  fatty  bodies  of  the  joints  and  bursas,  and 


70 


Osteology. 


which  have  been  supposed  to  be  the  ducts  of 
glands  lodged  within  the  masses  of  fat,  we 
are  not  able  to  discover  any  glandular  appear- 
ance within  them.  And  although  we  observe 
many  vessels  dispersed  upon  the  membranes 
of  the  fatty  bodies  and  fimbrise  ; and  that  we 
cannot  doubt  that  these  fimbriae  consist  of  ducts 
which  contain  a lubricating  liquor,  and  can 
even  press  such  a liquor  from  them  ; yet  their 
cavities  and  orifices  are  so  minute,  that  they 
are  not  discoverable  even  by  the  assistance 
of  magnifying-glasses.  These  fimbria;  appear, 
therefore,  to  be  ducts  like  those  of  the  ure- 
thra, which  prepare  a mucilaginous  liquor, 
without  the  assistance  of  any  knotty  or  glan- 
dular organ. 

Upon  the  whole,  the  synovia  seems  to  be 
furnished  by  invisible  exhalent  arteries  by  the 
ducts  of  the  fimbrise,  and  by  oil  exuding  from 
the  adipose  follicles  by  passages  not  yet  disco- 
vered. 

The  word  skeleton , which  by  its  etymology 
implies  simply  a dry  preparation,  is  usually 
applied  to  an  assemblage  of  all  the  bones  of 
an  animal  united  together  in  their  natural  or- 
der. It  is  said  to  be  a natural  skeleton,  when 
the  bones  are  connected  together  by  their  own 
proper  ligaments ; and  an  artificial  one,  when 
they  are  joined  by  any  other  substance,  as 
wire,  &c. 

The  skeleton  is  generally  divided  into  the 
head,  trunk,  and  extremities.  The  first  divi- 
sion includes  the  bones  of  the  cranium  and 
face.  The  bones  of  the  trunk  are  the  spine, 
ribs,  sternum,  and  bones  of  the  pelvis. 


Osteology. 


71 


The  upper  extremity  on  each  side  consists 
of  the  two  bones  of  the  shoulder,  viz.  the  sca- 
pula and  clavicle  ; the  bone  of  the  arm,  or  os 
humeri ; the  bones  of  the  fore-arm,  and  those 
of  the  hand. 

The  lower  extremity  on  each  side  of  the 
trunk  consists  of  the  thigh-bone  and  the  bones 
of  the  leg  and  foot. 


Sect.  II.  Of  the  Bones  of  the  Head. 

The  head  is  of  a roundish  figure,  and  some- 
what oval.*  Its  greatest  diameter  is  from  the 
forehead  to  the  occiput ; its  upper  part  is  call- 
ed vertex,  or  crown  of  the  head ; its  anterior 
or  fore-part  the  face  ; and  the  upper  part  of 
this  sinciput , or  forehead ; its  sides  the  tem- 
ples ; its  posterior,  or  hind-part,  the  occiput; 
and  its  inferior  part  the  basis . 

The  bones  of  the  head  may  be  divided  into 
those  of  the  cranium  and  face. 


* The  bones  of  the  foetus  being  perfectly  distinct,  and  the 
muscles  in  young  persons  not  acting  much,  the  shape  of  the 
head  has  been  supposed  to  depend  much  on  the  management  of 
children  when  very  young.  Vesalius,  who  has  remarked  the  dif- 
ference in  people  of  different  nations,  observes,  for  instance,  that 
■the  head  of  a Turk  is  conical,  from  the  early  use  of  the  turban  ; 
whilst  that  of  an  Englishman  is  flattened  by  the  chin-stay.  Some 
of  the  latest  physiologists  suppose,  with  good  reason,  that  this 
difference  is  chiefly  owing  to  certain  natural  causes  with  which 
we  are  as  yet  unacquainted. 


72 


Osteology. 


1.  Bones  of  the  Cranium  and  Face. 

There  are  eight  bones  of  the  cranium,  viz. 
the  coronal  bone,  or  os  frontis  ; the  two  pari- 
etal bones,  or  ossa  bregmatis ; the  os  occipi- 
tis ; the  two  temporal  bones ; the  sphenoid 
bone  ; and  the  os  ethmoides,  or  cribriforme. 

Of  these,  only  the  os  occipitis  and  ossa 
bregmatis  are  considered  as  proper  to  the  cra- 
nium ; the  rest  being  common  both  to  the  cra- 
nium and  face. 

These  bones  are  all  harder  at  their  surface 
than  in  their  middle  ; and  on  this  account  they 
are  divided  into  two  tables,  and  a middle  spon- 
gy substance  called  cliploe. 

In  this,  as  in  all  the  other  bones,  we  shall 
consider  its  figure,  structure,  processes,  de- 
pressions, and  cavities ; and  the  manner  in 
which  it  is  articulated  with  the  other  bones. 

The  os  frontis  has  some  resemblance  in 
shape  to  the  shell  of  the  cockle.  Externally  it 
is  convex,  its  concave  side  being  turned  to- 
wards the  brain.  This  bone,  in  the  places 
where  it  is  united  to  the  temporal  bones,  is 
very  thin,  and  has  there  no  diploe.  It  is  like- 
wise exceedingly  thin  in  that  part  of  the  orbit 
of  the  eye  which  is  nearest  to  the  nose.  Hence 
it  is,  that  a wound  in  the  eye,  by  a sword  or 
any  other  pointed  instrument,  is  sometimes 
productive  of  immediate  death.  In  these  cases, 
the  sword  passing  through  the  weak  part  of 
the  bone,  penetrates  the  brain,  and  divides 
the  nerves  at  their  origin ; or  perhaps  opens 


Osteology . 73 

some  blood-vessel,  the  consequences  of  which 
are  soon  fatal. 

We  observe  on  the  exterior  surface  of  this 
bone  five  apophyses  or  processes,  which  are 
easily  to  be  distinguished.  One  of  these  is 
placed  at  the  bottom  and  narrowest  part  of  the 
bone,  and  is  called  the  nasal  process,  from  its 
supporting  the  upper  end  of  the  bones  of  the 
nose.  The  four  others  are  called  angular  or 
orbitar  processes.  They  assist  to  form  the 
orbits,  which  are  the  cavities  on  which  the 
eyes  are  placed.  In  each  of  these  orbits  there 
are  two  processes,  one  at  the  interior  or  great 
angle,  and  the  other  at  the  exterior  or  little 
angle  of  the  orbit.  They  are  called  the  angu- 
lar processes.  Between  these  a ridge  is  ex- 
tended in  form  of  an  arch,  and  on  this  the  eye- 
brows are  placed.  It  is  called  the  orbitar  or 
superciliary  ridge,  and  in  some  measure  covers 
and  defends  the  globe  of  the  eye.  There  is  a 
hole  in  this  for  the  passage  of  the  frontal  ves- 
sels and  nerves.  This  arch  is  interrupted 
near  the  nose  by  a small  pit,  in  which  the  ten- 
don of  the  musculus  obliquus  major  of  the 
eye  is  fixed.  From  the  under  part  of  each  su- 
perciliary ridge  a thin  plate  runs  a considera- 
ble way  backwards,  and  has  the  name  of  orbi- 
tar ; the  external  and  fore-part  of  this  plate 
forms  a sinuosity  for  lodging  the  lacrymal 
gland.  Between  the  orbitar  plates  there  is  a 
large  discontinuation  of  the  bone,  which  is  fill- 
ed up  by  the  cribriform  part  of  the  os  ethmoi- 
des. 


K 


74 


Osteology. 


On  examining  the  inner  surface  of  this  bone 
at  its  under  and  middle  part,  we  observe  an 
elevation  in  form  of  a ridge,  which  has  been 
called  the  spinous  process  ; it  ascends  for  some 
way,  dividing  the  bone  into  two  considerable 
fossas,  in  which  the  anterior  lobes  of  the  brain 
are  placed.  To  a narrow  furrow  in  this  ridge 
is  attached  the  extremity  of  the  falx,  as  the 
membrane  is  called,  which  divides  the  brain 
into  two  hemispheres.  The  furrow  becoming 
gradually  wider,  is  continued  to  the  upper  and 
back  part  of  the  bone.  It  has  the  falx  fixed  to 
it,  and  part  of  the  longitudinal  sinus  lodged  in 
it.  Besides  the  two  fossse,  there  are  many 
depressions,  which  appear  like  digital  impres- 
sions, and  owe  their  formation  to  the  promi- 
nent circumvolutions  of  the  brain. 

In  the  foetus,  the  forehead  is  composed  of 
two  distinct  bones  ; so  that  in  them  the  sagit- 
tal suture  reaches  from  the  os  occipitis  to  the 
nose.  This  bone  is  almost  every  where  com- 
posed of  two  tables  and  a diploe.  These  two 
tables  separating  from  each  other  under  the 
eyes,  form  two  cavities,  one  on  each  side  of 
the  face,  called  the  frontal  sinuses.  These 
sinuses  are  lined  with  a soft  membrane,  called 
membrana  pituitaria.  In  these  sinuses  a mu- 
cus is  secreted,  which  is  constantly  passing 
through  two  small  holes  into  the  nostrils,  which 
it  serves  to  moisten. 

The  os  frontis  is  joined  by  suture  to  many 
of  the  bones  of  the  head,  viz.  to  the  parietal, 
maxillary,  and  temporal  bones  ; to  the  os  eth- 
moides  ; os  sphenoides ; os  unguis  ; and  ossa 


Osteology. 


75 


nasi.  The  suture  which  connects  it  with  the 
parietal  bones  is  called  the  coronal  suture. 

The  parietal  bones  are  two  in  number ; -they 
are  very  thin,  and  even  transparent  in  some 
places,  the  particular  figure  of  each  of  these 
bones  is  that  of  an  irregular  square,  bordered 
with  indentations  through  its  whole  circumfer- 
ence, except  at  its  lower  part.  It  will  be  ea- 
sily conceived,  that  these  bones  which  com- 
pose the  superior  and  lateral  parts  of  the  cra- 
nium, and  cover  the  greatest  part  of  the  brain, 
form  a kind  of  vault.  On  their  inner  surface 
we  observe  the  marks  of  the  vessels  of  the  du- 
ra mater ; and  at  their  upper  edge  the  groove 
for  the  superior  longitudinal  sinus. 

The  ossa  parietalia  are  joined  to  each  other 
by  the  sagittal  suture  ; to  the  os  sphenoides 
and  ossa  temporum  by  the  squamous  suture  ; 
to  the  os  occipitis  by  the  lambdoidal  suture,* 
so  called  from  its  resemblance  to  the  Greek 
letter  lambda  ; and  to  the  os  frontis  by  the  co- 
ronal suture. 

In  the  foetus,  the  parietal  bones  are  sepa- 
rated from  the  middle  of  the  divided  os  frontis 
by  a portion  of  the  cranium  then  unossified. 

The  occipital  bone  forms  the  posterior  and 
inferior  parts  of  the  skull ; it  approaches  near- 
ly to  the  shape  of  a lozenge,  and  is  indented 
throughout  three  parts  of  its  circumference. 

* The  lambdoidal  suture  is  sometimes  very  irregular,  being 
composed  of  many  small  sutures,  which  surround  so  many  lit- 
tle bones  called  ossa  triquetra , though  perhaps  improperly,  as 
they  are  not  always  triangular. 


76 


Osteology. 


There  is  a considerable  hole  in  the  inferior 
portion  of  this  bone,  called  the  foramen  mag- 
num, through  which  the  medulla  oblongata 
passes  into  the  spine. — The  nervi  accessorii, 
and  vertebral  arteries,  likewise  pass  through 
it.  Behind  the  condyles  are  two  holes  for  the 
passage  of  cervical  veins  into  the  lateral  si- 
nuses ; and  above  them  are  two  others  for\the 
passage  of  the  eighth  pair  and  accessory  nerves 
out  of  the  head.  At  the  sides,  and  a little  on 
the  anterior  part  of  the  foramen  magnum,  are 
two  processes,  called  the  condyles,  one  on 
each  side  ; they  are  of  an  oval  figure,  and  are 
covered  with  cartilage. 

The  external  surface  of  this  bone  has  a 
large  transverse  arched  ridge,  under  which  the 
bone  is  very  irregular,  where  it  affords  attach- 
ment to  several  muscles.  On  examining  its 
inner  surface,  we  may  observe  two  ridges  in 
form  of  a cross ; one  ascending  from  near  the 
foramen  magnum  to  the  top  of  the  bone ; the 
upper  end  of  this  in  which  the  falx  is  fixed,  is 
hollow,  for  lodging  the  superior  longitudinal 
sinus,  and  the  under  end  has  the  third  process 
of  the  dura  mater  fixed  to  it.  The  other  ridge, 
which  runs  horizontally,  is  likewise  hollow  for 
containing  the  lateral  sinuses.  Four  fossse 
are  formed  by  the  cross,  two  above  and  two 
below.  In  the  former  are  placed  the  posterior 
lobes  of  the  brain,  and  in  the  latter  the  lobes 
of  the  cerebellum. 

At  the  basis  of  the  cranium,  we  observe 
the  cuneiform  process  (which  is  the  name 
given  to  the  great  apophysis  at  the  fore  part  of 


Osteology.  77 

this  bone) ; it  serves  for  the  reception  of  the 
medulla  oblongata. 

The  os  occipitis  is  of  greater  strength  and 
thickness,  than  either  of  the  other  bones  of 
the  head,  though  irregularly  so ; at  its  inferi- 
or part,  where  it  is  thinnest,  it  is  covered  by 
a great  number  of  muscles. 

This  bone,  from  its  situation,  being  more 
liable  to  be  injured  by  falls,  than  any  other 
bone  of  the  head,  nature  has  wisely  given  it 
the  greatest  strength  at  its  upper  part,  where 
it  is  most  exposed  to  danger. 

It  is  joined  to  the  parietal  bones  by  the 
lambdoidal  suture,  and  to  the  ossa  temporum, 
by  the  additamentum  of  the  temporal  suture. 
It  is  likewise  connected  to  the  os  sphenoides 
by  the  cuneiform  process.  It  is  by  means  of 
the  os  occipitis  that  the  head  is  united  to  the 
trunk,  the  two  condyles  of  this  bone  being 
connected  to  the  superior  oblique  processes 
of  the  first  vertebra  of  the  neck. 

There  are  two  temporal  bones,  one  on  each 
side. — We  may  distinguish  in  them  two  parts; 
one  of  which  is  called  the  squamous  or  scaly 
part , and  the  other  pars  petrosa  from  its  hard- 
ness. This  last  is  shaped  like  a pyramid. 

Each  of  these  divisions  affords  processes 
and  cavities : externally  there  are  three  pro- 
cesses ; one  anterior,  called  the  zygomatic 
process  ; one  posterior,  called  the  mastoid  or 
mamillary  process , from  its  resemblance  to  a 
nipple  ; and  one  inferior,  called  the  styloid  pro- 
cess, because  it  is  shaped  like  a stiletto,  or  dag- 
ger. 


78 


Osteology. 


The  cavities  are,  1.  The  meatus  auditorius 
externus.  2.  A large  fossa  which  serves  for 
the  articulation  of  the  lower  jaw  ; it  is  before 
the  meatus  auditorius,  and  immediately  under 
the  zygomatic  process.  3.  The  stylo-mastoid 
hole,  so  called  from  its  situation  between  the 
styloid  and  mastoid  processes ; it  is  likewise 
styled  the  aquaeduct  of  Fallopius,  and  affords 
a passage  to  the  portio  dura  of  the  auditory, 
or  seventh  pair  of  nerves.  4.  Below,  and  on 
the  fore-part  of  the  last  foramen,  we  observe 
part  of  the  jugular  fossa,  in  which  the  begin- 
ning of  the  internal  jugular  vein  is  lodged.  An- 
terior and  superior  to  this  fossa  is  the  orifice 
of  a foramen  through  which  passes  the  carotid 
artery.  This  foramen  runs  first  upwards  and 
then  forwards,  forming  a kind  of  elbow,  and  ter- 
minates at  the  end  of  the  os  petrosum. — At  this 
part  of  each  temporal  bone,  we  may  observe 
the  opening  of  the  Eustachian  tube,  a canal 
which  passes  from  the  ear  to  the  back  part  of 
the  nose. 

In  examining  the  internal  surface  of  these 
bones,  we  may  remark  the  triangular  figure 
of  their  petrous  part  which  separates  two  fos- 
sae ; one  superior  and  anterior  ; the  other  in- 
ferior and  posterior:  the  latter  of  these  com- 
poses part  of  the  fossa,  in  which  the  cerebel- 
lum is  placed  ; and  the  former,  a portion  of 
the  least  fossa  for  the  basis  of  the  brain.  On 
the  posterior  side  of  the  pars  petrosa,  we  ob- 
serve the  meatus  auditorius  internus,  into 
which  enters  the  double  nerve  of  the  seventh 
pair.  On  the  under  side  of  this  process,  part 
of  a hole  appears,  which  is  common  to  the 


Osteology. 


79 


temporal  and  occipital  bones ; through  it  the 
lateral  sinus,  the  eighth  pair,  and  accessory- 
nerves,  pass  out  of  the  head. 

The  pars  petrosa  contains  several  little 
bones  called  the  bones  of  the  ear ; which,  as 
they  do  not  enter  into  the  formation  of  the 
cranium,  shall  be  described  when  we  are  treat- 
ing of  the  organs  of  hearing. 

The  ossa  temporum  are  joined  to  the  ossa 
malarum,  by  the  zygomatic  sutures  ; to  the  pa- 
rietal bones,  by  the  squamous  sutures  ; to  the 
os  occipitis,  by  the  lambdoidal  suture  ; and  to 
the  sphenoid  bone,  by  the  suture  of  that  name. 

This  bone,  from  its  situation  amidst  the 
other  bones  of  the  head,  has  sometimes  been 
called  cuneiforme . It  is  of  a very  irregular 
figure,  and  has  been  compared  to  a bat  with 
its  wings  extended. 

It  is  commonly  divided  into  its  middle  part 
or  body,  and  its  sides  or  wings. 

The  fore  part  of  the  body  has  a spine  or 
ridge,  which  makes  part  of  the  septum  nari- 
um.  The  upper  part  of  each  wing  forms  a 
share  of  the  temple.  The  fore  part  of  this 
belongs  to  the  orbit ; while  the  under  and 
back  part,  termed  spinous  process , is  lodged 
in  the  base  of  the  skull  at  the  point  of  the 
pars  petrosa.  But  two  of  the  most  remarka- 
ble processes  are  the  ptergoid  or  aliform,  one 
on  each  side  of  the  body  of  the  bone,  and  at 
no  great  distance  from  it.  Each  of  these  pro- 
cesses is  divided  into  two  wings,  and  of  these 
the  exterior  one  is  the  widest.  The  other  ter- 
minates in  a hook-like  process. 


80 


Osteology. 


The  internal  surface  of  this  bone  affords 
three  fossse.  Two  of  these  are  formed  by  the 
wings  of  the  bone,  and  make  a part  of  the 
lesser  fossae  of  the  basis  of  the  cranium.  The 
third,  which  is  smaller,  is  on  the  top  of  the- 
body  of  the  bone  ; and  is  called  sella  turcica , 
from  its  resemblance  to  a Turkish  saddle. 
This  fossa,  in  which  the  pituitary  gland  is 
placed,  has  posteriorly  and  anteriorly  process- 
es called  the  clinoid  processes. 

There  are  twelve  holes  in  this  bone,  viz.  six 
on  each  side.  The  first  is  the  passage  of  the 
optic  nerve  and  ocular  ar,tery ; the  second,  or 
large  slit,  transmits  the  third,  fourth,  sixth, 
and  first  part  of  the  fifth  pair  of  nerves  with 
the  ocular  vein ; the  third  hole  gives  passage 
to  the  second  branch  of  the  fifth  pair ; and  the 
fourth  hole  to  the  third  branch  of  the  fifth 
pair  of  nerves.  The  fifth  hole  is  the  passage 
of  the  artery  of  the  dura  mater.  The  sixth 
hole  is  situated  above  the  ptergoid  process  of 
the  sphenoid  bone;  through  it  a reflected 
branch  of  the  second  part  of  the  fifth  pair 
passes. 

Within  the  substance  of  the  os  sphenoides 
there  are  two  sinuses  separated  by  a bony 
plate.  They  are  lined  with  the  pituitary  mem- 
brane ; and,  like  the  frontal  sinuses,  separate 
a mucus  which  passes  into  the  nostrils. 

The  os  sphenoides  is  joined  to  all  the  bones 
of  the  cranium  ; and  likewise  to  the  ossa  max- 
illaria,  ossa  malarum,  ossa  palati,  and  vo- 
mer. 


Osteology. 


81 


This  bone  makes  part  of  the  basis  of  the 
skull,  assists  in  forming  the  orbits,  and  affords 
attachment  to  several  muscles. 

The  os  ethmoides  is  situated  at  the  fore 
part  of  the  basis  of  the  cranium,  and  is  of  a 
very  irregular  figure.  From  the  great  number 
of  holes  with  which  it  is  pierced,  it  is  some- 
times called  os  cribriforme  or  sieve-like  bone. 

It  consists  of  a middle  part  and  two  sides. 
The  middle  part  is  formed  of  a thin  bony 
plate,  in  which  are  an  infinite  number  of  holes 
that  afford  a passage  to  filaments  of  the  ol- 
factory nerve,  From  the  middle  of  this  plate, 
both  on  the  outside  and  from  within,  there 
rises  up  a process,  which  may  be  easily 
distinguished.  The  inner  one  is  called  cris- 
ta galli , from  its  supposed  resemblance  to 
a cock’s  comb.  To  this  process  the  falx  of 
the  dura  mater  is  attached.  The  exterior  pro- 
cess, which  has  the  same  common  basis  as  the 
crista  galli,  is  a fine  lamella  which  is  united 
to  the  vomer;  and  divides  the  cavity  of  the 
nostrils,  though  unequally,  it  being  generally 
a little  inclined  to  one  side. 

The  lateral  parts  of  this  bone  are  compos- 
ed of  a cellular  substance  ; and  these  cells  are 
so  very  intricate,  that  their  figure  or  number 
cannot  be  described.  Many  writers  have  on 
this  account  called  this  part  of  the  bone  the 
labyrinth.  These  cells  are  externally  covered 
with  a very  thin  bony  lamella.  This  part  of 
the  bone  is  called  the  os  planum , and  forms 
part  of  the  orbit. 


82 


Osteology. 


The  different  cells  of  this  bone,  which  are 
numerous,  and  which  are  every  where  lined 
with  the  pituitary  membrane,  evidently  serve 
to  enlarge  the  cavity  of  the  nose,  in  which  the 
organ  of  smelling  resides. 

This  bone  is  joined  to  the  os  sphenoides, 
os  frontis,  ossa  maxillaria,  ossa  palati,  ossa 
nasi,  ossa  unguis,  and  vomer. 

The  ancients,  who  considered  the  brain  as 
the  seat  of  all  the  humours,  imagined  that 
this  viscus  discharged  its  redundant  moisture 
through  the  holes  of  the  ethmoid  bone.  And 
the  vulgar  still  think,  that  abscesses  of  the 
brain  discharge  themselves  through  the  mouth 
and  ears,  and  that  snuff  is  liable  to  get  into 
the  head ; but  neither  snuff  nor  the  matter  of 
an  abscess  are  more  capable  of  passing 
through  the  cribriform  bone,  than  the  serosi- 
ty  which  they  supposed  was  discharged 
through  it  in  a common  cold. — All  the  holes 
of  the  ethmoid  bone  are  filled  up  with  the 
branches  of  the  olfactory  nerve.  Its  inner 
part  is  likewise  covered  with  the  dura  mater, 
and  its  cells  are  every  where  lined  with  the 
pituitary  membrane  ; so  that  neither  matter 
nor  any  other  fluid  can  possibly  pass  through 
this  bone  either  externally  or  internally.  Mat- 
ter is  indeed  sometimes  discharged  through 
the  nostrils ; but  the  seat  of  the  disease  is  in 
the  sinuses  of  the  nose,  and  not  in  the  brain ; 
and  imposthumations  are  observed  to  take  place 
in  the  ear,  which  suppurate  and  discharge 
themselves  externally. 


Osteology. 


83 


Before  we  leave  the  bones  of  the  head,  we 
wish  to  make  some  general  observations  on  its 
structure  and  figure. — As  the  cranium  might 
have  been  composed  of  a single  bone,  the  ar- 
ticulation of  its  several  bones  being  absolute- 
ly without  motion,  it  may  be  asked  perhaps, 
Why  such  a multiplicity  of  bones,  and  so 
great  number  of  sutures  ? Many  advantages 
may  possibly  arise  from  this  plurality  of  bones 
and  sutures,  which  may  not  yet  have  been 
observed.  We  are  able,  however,  to  point 
out  many  useful  ends,  which  could  only  be  ac- 
complished by  this  peculiarity  of  structure. — 
In  this,  as  in  all  the  other  works  of  nature,  the 
great  wisdom  of  the  Creator  is  evinced,  and  can- 
not fail  to  excite  our  admiration  and  gratitude. 

The  cranium,  by  being  divided  into  sever- 
al bones,  grows  much  faster  and  with  greater 
facility,  than  if  it  was  composed  of  one  piece 
only.  In  the  foetus,  the  bones,  as  we  have 
before  observed,  are  perfectly  distinct  from 
each  other.  The  ossification  begins  in  the 
middle  of  each  bone,  and  proceeds  gradually 
to  the  circumference.  Hence  the  ossification, 
and  of  course  the  increase  of  the  head,  is  car- 
ried on  from  an  infinite  number  of  points  at 
the  same  time,  and  the  bones  consequently  ap- 
proach each  other  in  the  same  proportion.  To 
illustrate  this  doctrine  more  clearly,  if  it  can 
want  further  illustration,  suppose  it  necessa- 
ry for  the  parietal  bones  which  compose  the 
upper  part  of  the  head,  to  extend  their  ossifi- 
cation, and  form  the  fore  part  of  the  head 
likewise. — Is  it  not  evident,  that  this  process 


84 


Osteology. 


would  be  much  more  tedious  than  it  is  now, 
when  the  os  frontis  and  the  parietal  bones  are 
both  growing  at  the  same  time?  Hence  it  hap- 
pens, that  the  Heads  of  young  people,  in  which 
the  bones  begin  to  touch  each  other,  increase 
slowly  ; and  th*t  the  proportionate  increase  of 
the  volume  of  the  head  is  greater  in  three 
months  in  the  foetus,  than  it  is  perhaps  in 
twenty  four  months  at  the  age  of  fourteen  or 
fifteen  years. 

The  sutures,  exclusive  of  their  advantage 
in  suspending  the  processes  of  the  dura  ma- 
ter, are  evidently  of  great  utility  in  prevent- 
ing the  too  great  extent  of  fractures  of  the 
skull. — Suppose,  for  instance,  that  by  a fall 
or  blow,  one  of  the  bones  of  the  cranium  be- 
comes fractured.  The  fissure,  which  in  a 
head  composed  of  only  one  bone,  would  be 
liable  to  extend  itself  through  the  whole  of  it, 
is  checked,  and  sometimes  perhaps  stopped  by 
the  first  suture  it  meets,  and  the  effects  of 
the  injury  are  confined  to  the  bone  on  which 
the  blow  was  received.  Ruysch  indeed,  and 
some  others,  will  not  allow  the  sutures  to  be 
of  any  such  use  ; but  cases  have  been  met 
with  where  they  seemed  to  have  had  this  ef- 
fect, and  in  young  subjects  their  utility  irl 
this  respest  must  be  still  more  obvious* 

The  spherical  shape  of  the  head  seems  like- 
wise to  render  it  more  capable  of  resisting  ex- 
ternal violence  than  any  other  shape  would  do. 
In  a vault,  the  parts  mutually  support  and 
strengthen  each  other,  and  this  happens  in  the 
cranium. 


Osteology . 


85 


2.  Proper  Bones  of  the  Face. 

The  face,  which  consists  of  a great  number 
of  bones,  is  commonly  divided  into  the  upper 
and  lower  jaws.  The  upper  jaw  consists  of 
thirteen  bones,  exclusive  of  the  teeth.  Of 
these,  six  are  placed  on  each  side  of  the  max- 
illa superior,  and  one  in  the  middle. 

The  bones,  which  are  in  pairs,  are  the  os- 
sa malarum,  ossa  maxillaria,  ossa  nasi,  ossa 
unguis,  ossa  palati,  and  ossa  spongiosa  inferi- 
ora.  The  single  bone  is  the  vomer. 

These  are  the  prominent  square  bones  which 
are  placed  under  the  eyes,  forming  part  of 
the  orbits  and  the  upper  part  of  the  cheeks. 
Each  of  them  affords  three  surfaces  ; one  ex- 
terior and  a little  convex  ; a second  superior 
and  concave,  forming  the  inferior  part  and 
sides  of  the  orbit ; and  a third  posterior,  irre- 
gular, and  hollowed  for  the  lodgment  of  the 
lower  part  of  the  temporal  muscle: 

The  angles  of  each  bone  form  four  process- 
es, two  of  which  may  be  called  orbitar  process- 
es ; of  these  the  upper  one  is  joined  by  suture 
to  the  os  frontis,  and  that  below  to  the  maxil- 
lary bone.  The  third  is  connected  with  the 
os  sphenoides  by  means  of  the  transverse  su- 
ture ; and  the  fourth  is  joined  to  the  zygoma- 
tic process  of  the  temporal  bone,  with  which 
it  forms  the  zygoma. 

These  bones,  which  are  of  a very  irregular 
figure,  are  so  called  because  they  form  the 
most  considerable  portion  of  the  upper  jaw. 


86 


Osteology. 


They  are  two  ill  number,  and  generally  re- 
main distinct  through  life. 

Of  the  many  processes  which  are  to  be 
seen  on  these  bones,  and  which  are  connect- 
ed with  the  bones  of  the  face  and  skull,  we 
shall  describe  only  the  most  remarkable. 

One  of  these  processes  is  at  the  upper  and 
fore  part  of  the  bone,  making  part  of  the  side 
of  the  nose,  and  called  the  nasal  process.  An- 
other forms  a kind  of  circular  sweep  at  the  in- 
ferior part  of  the  bone,  in  which  are  the  alve- 
oli or  sockets  for  the  teeth : this  is  called  the 
alveolar  process.  A third  process  is  united  to 
the  os  malse  on  each  side.  Between  this  and 
the  nasal  process  there  is  a thin  plate,  which 
forms  a share  of  the  orbit,  and  lies  over  a 
passage  for  the  superior  maxillary  vessels  and 
nerves. — The  alveolar  process  has  posterior- 
ly a considerable  tuberosity  on  its  internal 
surface,  called  the  maxillary  tuberosity. 

Behind  the  alveolar  process  we  observe  two 
horizontal  lamellae,  which  uniting  together, 
form  a part  of  the  roof  of  the  mouth,  and  di- 
vide it  from  the  nose.  The  hollowness  of  the 
roof  of  the  mouth  is  owing  to  this  partition’s 
being  seated  somewhat  higher  than  the  alveo- 
lar process.— -At  the  fore  part  of  the  horizon- 
tal lamellae  there  is  a hole  called  foramen  inci - 
sivum , through  which  small  blood-vessels  and 
nerves  go  between  the  mouth  and  nose. 

In  viewing  these  bones  internally,  we  ob- 
serve a fossa  in  the  inferior  portion  of  the 
nasal  process,  which  with  the  os  unguis  and 


Osteology. 


87 


os  spongiosum  inferius,  forms  a passage  for 
the  lachrymal  duct. 

Where  these  two  bones  are  united  to  each 
other,  they  project  somewhat  upwards  and 
forwards,  leaving  between  them  a furrow,  in- 
to which  the  lower  portion  of  the  septum  na- 
si is  admitted. 

Each  of  these  bones  being  hollow,  a consi- 
derable sinus  is  formed  under  its  orbitar  part. 
This  cavity,  which  is  usually  named  after 
Highmore,  though  it  was  described  by  Fallopi- 
us and  others  before  his  time,  is  lined  with 
the  pituitary  membrane.  It  is  intended  for 
the  same  purposes  as  the  other  sinuses  of  the 
nose,  and  opens  into  the  nostrils. 

The  ossa  maxillaria  are  connected  with  the 
greater  part  of  the  bones  of  the  face  and  crani- 
um, and  assist  in  forming  not  only  the  cheeks, 
but  likewise  the  palate,  nose,  and  orbits. 

The  ossa  nasi  form  two  irregular  squares. 
They  are  thicker  and  narrower  above  than 
below.  Externally  they  are  somewhat  convex, 
and  internally  slightly  concave.  These  bones 
constitute  the  upper  part  of  the  nose.  At 
their  fore  part  they  are  united  to  each  other, 
above  to  the  os  frontis,  by  their  sides  to  the 
ossa  maxillaria  superiora,  posteriorly  and  in- 
teriorly to  the  septum  narium,  and  below  to 
the  cartilages  that  compose  the  rest  of  the 
nostrils. 

These  little  transparent  bones  owe  their 
name  to  their  supposed  resemblance  to  a fin- 
ger-nail. Sometimes  they  are  called  ossa  la - 
chrymalia 5 from  their  concurring  with  the  na- 


88 


Osteology. 


sal  process  of  each  maxillary  bone  in  forming 
a lodgement  for  the  lachrymal  sac  and  duct. 

The  ossa  unguis  are  of  an  irregular  figure. 
Their  external  surface  consists  of  two  smooth 
parts,  divided  by  a middle  ridge.  One  of  these 
parts,  which  is  concave  and  nearest  to  the 
nose,  serves  to  support  the  lachrymal  sac  and 
part  of  the  lachrymal  duct.  The  other,  which 
is  flat,  forms  a small  part  of  the  orbit. 

Each  of  these  bones  is  connected  with  the 
os  frontis,  os  ethmoides,  and  os  maxillare  su- 
pe  rius. 

These  bones  which  are  situated  at  the  back 
part  of  the  roof  of  the  mouth,  between  the  os 
sphenoides  and  the  ossa  maxillaria  superiora, 
are  of  a very  irregular  shape,  and  serve  to 
form  the  nasal  and  maxillary  fossa,  and  a small 
portion  of  the  orbit.  Where  they  are  united 
to  each  other,  they  rise  up  into  a spine  on 
their  internal  surface.  This  spine  appears  to 
be  a continuation  of  that  of  the  superior  max- 
illary holies,  and  helps  to  form  the  septum 
narium. 

These  bones  are  joined  to  the  ossa  maxilla- 
ria superiora,  os  ethmoides,  os  sphenoides, 
and  vomer. 

This  bone  derives  its  name  from  its  resem- 
blance to  a ploughshare.  It  is  a long  and  flat 
bone,  somewhat  thicker  at  its  back  than  at  its 
fore  part.  At  its  upper  part  we  observe  a 
furrow  extending  through  its  whole  length. 
The  posterior  and  largest  part  of  this  furrow 
receives  a process  of  the  sphenoid  bone.  From 
this  the  furrow  advances  forwards,  and  be- 


Osteology. 


89 


coming  narrower  and  shallower,  receives  some 
part  of  the  nasal  lamella  ethmoidea ; the  rest 
serves  to  support  the  middle  cartilage  of  the- 
nose. 

The  inferior  portion  of  this  bone  is  placed 
on  the  nasal  spine  of  the  maxillary  and  palate 
bones,  which  we  mentioned  in  our  description 
of  the  ossa  palati. 

The  vomer  is  united  to  the  os  sphenoides, 
os  ethmoides,  ossa  maxillaria  superiora,  and 
ossa  palati.  It  forms  part  of  the  septum  nari- 
um,  by  dividing  the  back  part  of  the  nose  into 
two  nostrils. 

The  parts  which  are  usually  described  by 
this  name,  do  not  seem  to  deserve  to  be  dis- 
tinguished as  distinct  hones,  except  in  young 
subjects.  They  consist  of  a spongy  lamella 
in  each  nostril,  which  is  united  to  the  spongy 
lamina  of  the  ethmoid  bone,  of  which  they 
are  by  some  considered  as  a part. 

Each  of  these  lamellae  is  longest  from  be- 
hind forwards  ; with  its  convex  surface  turn- 
ed towards  the  septum  narium,  and  its  con- 
cave part  towards  the  maxillary  bone,  covering 
the  opening  of  the  lachrymal  duct  into  the 
nose. 

These  bones  are  covered  with  the  pituitary 
membrane  ; and,  besides  their  connection  with 
the  ethmoid  bone,  are  joined  to  the  ossa  max- 
illaria superiora,  ossa  palati,  and  ossa  unguis. 

The  maxilla  inferior,  or  lower  jaw,  which 
in  its  shape  resembles  a horse-shoe,  consists 
of  two  distinct  bones  in  the  foetus  ; but  these 
unite  together  soon  after  birth,  so  as  to  form 

M 


90 


Osteology. 


only  one  bone.  The  upper  edge  of  this  bone, 
like  the  os  maxillare  superius,  has  an  alveolar 
process,  furnished  with  sockets  for  the  teeth. 

On  each  side  the  posterior  part  of  the  bone 
rises  almost  perpendicularly  into  two  process- 
es. The  highest  of  these,  called  the  coronoid 
process,  is  pointed  and  thin,  and  serves  for 
the  insertion  of  the  temporal  muscle.  The 
other,  or  condyloid  process,  as  it  is  called,  is 
shorter  and  thicker,  and  ends  in  an  oblong 
rounded  head,  which  is  received  into  a fossa 
of  the  temporal  bone,  and  is  formed  for  a 
moveable  articulation  with  the  cranium.  This 
joint  is  furnished  with  a moveable  cartilage. 
At  the  bottom  of  each  coronoid  process,  on 
its  inner  part,  we  observe  a foramen  extend- 
ing under  the  roots  of  all  the  teeth,  and  ter- 
minating at  the  outer  surface  of  the  bone  near 
the  chin.  Each  of  these  canals  transmits  an 
artery,  vein,  and  nerve,  from  which  branches 
are  sent  off  to  the  teeth. 

The  lower  jaw  is  capable  of  a great  variety 
of  motion.  By  sliding  the  condyles  from  the 
cavity  towards  the  eminences  on  each  side, 
we  bring  it  horizontally  forwards,  as  in  biting ; 
or  we  may  bring  the  condyles  only  forward, 
and  tilt  the  rest  of  the  jaw  backward,  as  in 
opening  the  mouth.  We  are  likewise  able  to 
slide  the  condyles  alternately  backwards  and 
forwards  from  the  cavity  to  the  eminence,  and 
vice  versa,  as  in  grinding  the  teeth.  The  car- 
tilages, by  adapting  themselves  to  the  differ- 
ent inequalities  in  these  several  motions  of  the 


Osteology. 


91 


jaw,  serve  to  secure  the  articulation,  and  to 
prevent  any  injuries  from  friction. 

The  alveolar  processes  are  composed  of  an 
outer  and  inner  bony  plate,  united  together  by 
thin  partitions,  which  at  the  fore  part  of  the 
jaw  divide  the  processes  into  as  many  sockets 
as  there  are  teeth.  But  at  the  back  part  of 
the  jaw,  where  the  teeth  have  more  than  one 
root,  we  find  a distinct  cell  for  each  root.  In 
both  jaws  these  processes  begin  to  be  formed 
with  the  teeth  ; they  likewise  accompany  them 
in  their  growth,  and  gradually  disappear  when 
the  teeth  are  removed. 

3.  Of  the  Teeth. 

The  teeth  are  bones  of  a particular  struc- 
ture, formed  for  the  purposes  of  mastication 
and  the  articulation  of  the  voice.  It  will  be 
necessary  to  consider  their  composition  and  fi- 
gure, their  number  and  arrangement,  and  the 
time  and  order  in  which  they  appear. 

In  each  tooth  we  may  distinguish  a body,  a 
neck,  and  a root  or  fangs. 

The  body  of  the  tooth  is  that  part  which 
appears  above  the  gums.  The  root  is  fixed 
into  the  socket,  and  the  neck  is  the  middle 
part  between  the  two. 

The  teeth  are  composed  of  two  substances, 
viz.  enamel  and  bone.  The  enamel,  or  the 
vitreous  or  cortical  part  of  the  tooth,  is  a 
white  and  very  hard  and  compact  substance 
peculiar  to  the  teeth,  and  appears  fibrous  o-r 


92 


Osteology. 


striated  when  broken.  This  substance  is  thick- 
est on  the  grinding  surface,  and  becoming  gra- 
dually thinner,  terminates  insensibly  at  the 
neck  of  the  tooth.  Ruysch* * * §  affirmed,  that  he 
could  trace  the  arteries  into  the  hardest  part 
of  the  teeth;  Lieweilhoeckf  suspected  the  fibres 
of  the  enamel  to  be  so  many  vessels  ; and 
Monro  f says,  he  has  frequently  injected  the 
vessels  of  the  teeth  in  children,  so  as  to 
make  the  inside  of  the  cortex  appear  perfectly 
red.  But  it  is  certain,  that  it  is  not  tinged  by 
a madder  diet,  and  that  no  injection  will  ever 
reach  it,  so  that  it  has  no  appearance  of  be- 
ing vascular  $. 

The  bony  part,  which  composes  the  inner 
substance  of  the  body,  neck,  and  root  of  the 
tooth,  resembles  other  bones  in  its  structure, 
but  it  is  much  harder  than  the  most  compact 
part  of  bones  in  general.  As  a tooth  when 
once  formed  receives  no  tinge  from  a madder 
diet,  and  as  the  minutest  injections  do  not  pe- 
netrate into  its  substance,  this  part  of  the 
tooth  has,  like  the  enamel,  been  supposed  not 
to  be  vascular.  But  when  we  consider  that 
the  fangs  of  a tooth  are  invested  by  a perios- 
teum, and  that  the  swellings  of  these  fangs 
are  analogous  to  the  swellings  of  other  bones, 
we  may  reasonably  conclude,  that  there  is  a 
similarity  of  structure ; and  that  this  bony 
part  has  a circulation  through  its  substance, 

* Thefaur  10  no.  27. 

■f  A.rcan.  Natur.  continuat.  Epiftol. 

f Anat  of  the  Human  Bones. 

§ Hunter  on  the  Teeth. 


Osteology. 


93 


although  from  its  hardness  we  are  unable  to 
demonstrate  its  vessels. 

In  each  tooth  we  find  an  inner  cavity,  into 
which  enter  an  artery,  vein,  and  nerve.  This 
cavity  begins  by  a small  opening,  and  becom- 
ing larger,  terminates  in  the  body  of  the  tooth. 
In  advanced  life  this  hole  sometimes  closes, 
and  the  tooth  is  of  course  rendered  insensible. 

The  periosteum  surrounds  the  teeth  from 
their  fangs  to  a little  beyond  their  bony  sock- 
ets, where  we  find  it  adhering  to  the  gums. 
This  membrane,  while  it  incloses  the  teeth, 
serves  at  the  same  time  to  line  the  sockets,  so 
that  it  may  be  considered  as  common  to  both. 

The  teeth  are  likewise  secured  in  their  sock- 
ets by  means  of  the  gums  ; a red,  vascular, 
firm,  and  elastic  substance,  that  possesses  but 
little  sensibility.  In  the  gums  of  infants  we 
find  a hard  ridge  extending  through  their 
whole  length,  but  no  such  ridge  is  to  be  seen 
in  old  people  who  have  lost  their  teeth. 

The  number  of  the  teeth  in  both  jaws  at  full 
maturity,  usually  varies  from  twenty-eight  to 
thirty-two.  They  are  commonly  divided  into 
three  classes,  viz.  incisores,  canini,  and  grind- 
ers or  molares.*  The  incisores  are  the  four 
teeth  in  the  fore  part  of  each  jaw.  They 
have  each  of  them  two  surfaces  ; one  anterior 

* Mr.  Hunter  has  thought  proper  to  vary  this  division.  He 
retains  the  old  name  of  incisores  to  the  four  fore  teeth,  but  he 
distinguishes  the  canine  teeth  by  the  name  of  the  cuspidafi.  The 
two  teeth  which  are  next  to  these,  and  which  have  been  usu- 
ally ranked  with  the  molares,  he  calls  the  bicuspides  ; and  he 
gives  the  name  of  grinders  only  to  the  three  last  teeth  on  each 
side. 


94 


Osteology. 


and  convex,  the  other  posterior  and  slightly 
concave,  both  of  which  terminate  in  a sharp 
edge.  They  are  called  incisores  from  their 
use  in  dividing  the  food.  They  are  usually 
broader  and  thicker  in  the  upper  than  in  the 
under  jaw;  and,  by  being  placed  somewhat 
obliquely,  generally  fall  over  the  latter. 

The  canini  derive  their  name  from  their  re- 
semblance to  a dog’s  tusks,  being  the  longest 
of  all  the  teeth.  We  find  one  on  each  side 
of  the  incisores,  so  that  there  are  two  canini 
in  each  jaw.  Their  fang  resembles  that  of  the 
incisores,  but  is  much  larger;  and  in  their 
shape  they  appear  like  an  incisor  with  its  edge 
worn  off,  so  as  to  terminate  in  a narrow  point. 

These  teeth  not  being  calculated  for  cutting 
and  dividing  the  food  like  the  incisores,  or  for 
grinding  it  like  the  molares,  seem  to  be  intend- 
ed for  laying  hold  of  substances.* 

The  molares  or  grinders,  of  which  there 
are  ten  in  each  jaw,  are  so  called,  because 
from  their  shape  and  size  they  are  fitted  for 
grinding  the  food.  Each  of  the  incisores  and 
canini  is  furnished  only  with  one  fang;  but  in 
the  molares  of  the  under  jaw  we  constantly 
find  two  fangs,  and  in  those  of  the  upper  jaw' 
three  fangs.  These  fangs  are  sometimes  se- 
parated into  two  points,  and  each  of  these  points 
has  sometimes  been  described  as  a distinct 
fang. 

* Mr.  Hunter  remarks  of  these  teeth,  that  we  may  trace  in 
them  a similiarity  in  shape,  situation,  and  use,  from  the  most 
imperfectly  carnivorous  animal,  which  we  believe  to  he  the  hu- 
man species,  to  the  lion,  which  is  the  most  perfectly  carnivo- 
rous. 


Osteology. 


95 


The  two  first  of  the  molares,  or  those  near- 
est to  the  canine  teeth  on  each  side,  differ 
from  the  other  three,  and  are  with  great  pro- 
priety named  bicuspides  by  Mr.  Hunter.  They 
have  sometimes  only  one  root,  and  seem  to  be 
of  a middle  nature  between  the  incisores  and 
the  larger  molares.  The  two  next  are  much 
larger.  The  fifth  or  last  grinder  on  each  side 
is  smaller  and  shorter  than  the  rest ; and  from 
its  not  cutting  the  gum  till  after  the  age  of 
twenty,  and  sometimes  not  till  much  later  in 
life,  is  called  dens  sapientice. 

There  is  in  the  structure  and  arrangement 
of  all  these  teeth  an  art  which  cannot  be  suf- 
ficiently admired.  To  understand  it  properly, 
it  will  be  necessary  to  consider  the  under  jaw 
as  a kind  of  lever,  with  its  fixed  points  at  its 
articulations  with  the  temporal  bones : — it  wiiL 
be  right  to  observe,  too,  that  its  powers  arise 
from  its  different  muscles,  but  in  elevation 
chiefly  from  the  temporalis  and  masseter;  and 
that  the  aliment  constitutes  the  object  of  re- 
sistance. It  will  appear,  then,  that  the  mola- 
res, by  being  placed  nearest  the  centre  of  mo- 
tion, are  calculated  to  press  with  a much 
greater  force  than  the  other  teeth,  independent 
of  their  grinding  powers  which  they  possess 
by  means  of  the  pterygoid  muscles ; and  that 
it  is  for  this  reason  we  put  between  them  any 
hard  body  we  wish  to  break. 

The  canini  and  incisores  are  placed  farther 
from  this  point,  and  of  course  cannot  exert  so 
much  force  ; but  they  are  made  for  cutting 
and  tearing  the  food,  and  this  form  seems  to 
make  amends  for  their  deficiency  in  strength. 


96 


Osteology . 


There  are  examples  of  children  who  have 
come  into  the  world  with  two,  three,  and  even 
four  teeth ; but  these  examples  are  very  rare ; 
and  it  is  seldom  before  the  seventh,  eighth, 
or  ninth  month  after  birth,  that  the  incisores, 
which  are  the  first  formed,  begin  to  pass 
through  the  gum.  The  symptoms  of  denti- 
tion, however,  in  consequence  of  irritation 
from  the  teeth,  frequently  take  place  in  the 
fourth  or  fifth  month. — About  the  twentieth 
or  twenty-fourth  month,  the  canini  and  two 
molares  make  their  appearance. 

The  dangerous  symptoms  that  sometimes 
accompany  dentition,  are  owing  to  the  pres- 
sure of  the  teeth  on  the  gum,  which  they  ir- 
ritate so  as  to  excite  pain  and  inflammation. 
This  irritation  seems  to  occasion  a gradual 
wasting  of  the  gum  at  the  part,  till  at  length 
the  tooth  makes  its  appearance. 

The  symptoms  are  more  or  less  alarming,  in 
proportion  to  the  resistance  which  the  gum 
affords  to  the  teeth,  and  according  to  the  num- 
ber of  teeth  which  may  chance  to  seek  a pas- 
sage at  the  same  time.  Were  they  all  to  ap- 
pear at  once,  children  would  fall  victims  to 
the  pain  and  excessive  irritation  ; but  Nature 
has  so  very  wisely  disposed  them,  that  they 
usually  appear  one  after  the  other,  with  some 
distance  of  time  between  each.  The  first  in- 
cisor that  appears  is  generally  in  the  lower 
jaw,  and  is  followed  by  one  in  the  upper  jaw. 
Sometimes  the  canini,  but  more  commonly  one 
of  the  molares,  begins  to  pass  through  the 
gum  first. 


Osteology. 


97 


These  20  teeth,  viz.  eight  incisores,  four 
canini,  and  eight  molares,  are  called  tempora- 
ry or  milk  teeth , because  they  are  all  shed  be- 
tween the  age  of  seven  and  fourteen,  and  are 
succeeded  by  what  are  called  the  permanent  or 
aclult  teeth.  The  latter  are  of  a firmer  texture, 
and  have  larger  fangs. 

These  adult  teeth  being  placed  in  a distinct 
set  of  alveoli,  the  upper  sockets  gradually  dis- 
appear, as  the  under  ones  increase  in  size,  till 
at  length  the  temporary,  or  upper  teeth,  hav- 
ing no  longer  any  support,  consequently  fall 
out. 

To  these  20  teeth,  which  succeed  the  tem- 
porary ones,  12  others  are  afterwards  added, 
viz.  three  molares  on  each  side  in  both  jaws: 
and  in  order  to  make  room  for  this  addition, 
we  find  that  the  jaws  gradually  lengthen  in 
proportion  to  the  growth  of  the  teeth  ; so  that 
with  20  teeth,  they  seem  to  be  as  completely 
filled  as  they  are  afterwards  with  32.  This  is 
the  reason  why  the  face  is  rounder  and  flatter 
in  children  than  in  adults. 

With  regard  to  the  formation  of  the  teeth, 
we  may  observe,  that  in  a fcetus  of  four  months, 
the  alveolar  process  appears  only  as  a shallow 
longitudinal  groove,  divided  by  minute  ridges 
into  a number  of  intermediate  depressions  ; in 
each  of  which  we  find  a small  pulpy  substance 
surrounded  by  a vascular  membrane.  This 
pulp  gradually  ossifies,  and  its  lower  part  is 
lengthened  out  to  form  the  fang.  When  the 
bony  part  of  the  tooth  is  formed,  its  surface 
begins  to  be  incrusted  with  the  enamel.  How 

N 


98 


Osteology. 


the  latter  is  formed  and  deposited,  we  are  not 
yet  able  to  determine. 

The  rudiments  of  some  of  the  adult  teeth 
begin  to  be  formed  at  a very  early  period,  for 
the  pulp  of  one  of  the  incisores  may  general- 
ly be  perceived  in  a foetus  of  eight  months, 
and  the  ossification  begins  in  it  soon  after  birth. 
The  first  bicuspis  begins  to  ossify  about  the 
fifth  or  sixth,  and  the  second  about  the  seventh 
year.  The  first  adult  grinder  cuts  the  gum 
about  the  12th,  the  second  about  the  18th,  and 
the  third,  or  dens  sapientice , usually  between 
the  20th  and  30th  year. 

The  teeth,  like  other  bones,  are  liable  to  be 
affected  by  disease.  Their  removal  is  like- 
wise the  natural  consequences  of  old  age ; for 
as  we  advance  in  life,  the  alveoli  fill  up, 
and  the  teeth,  especially  the  incisores,  fall  out. 
When  this  happens,  the  chin  projects  forward, 
and  the  face  is  much  shortened. 

4.  Of  the  Os  Hyoides .* 

The  os  hyoides,  which  is  placed  at  the  root 
of  the  tongue,  was  so  called  by  the  ancients 
on  account  of  its  supposed  resemblance  to 
the  Greek  letter  v. 


* This  hone  is  very  seldom  preserved  with  the  skeleton,  and 
cannot  be  included  among  the  bones  of  the  head,  or  any  other 
division  of  the  skeleton  Thomas  Bartholin  has  perhaps  very 
properly  described  it  among  parts  contained  in  the  mouth  ; but 
the  generality  of  anatomical  writers  have  placed  it,  as  it  is  here, 
after  the  bones  of  the  face. 


Osteology. 


99 


It  will  be  necessary  to  distinguish  in  it,  its 
body,  horns,  and  appendices. 

The  body,  which  is  the  middle  and  broad- 
est part  of  the  bone,  is  so  placed  that  it  may 
be  easily  felt  at  the  fore  part  of  the  throat. 
Anteriorly  it  is  irregularly  convex,  and  its  in- 
ner surface  is  unequally  concave.  Its  cornua, 
or  horns,  which  are  flat  and  a little  bent,  be- 
ing much  longer  than  the  body  part,  may  be 
described  as  forming  the  sides  of  the  «.  The 
appendices,  or  little  horns,  as  they  are  called 
by  M.  Windslow,  and  some  other  writers,  are 
two  processes  which  rise  up  from  the  articu- 
lations of  the  cornua  with  the  body,  and  are 
usually  connected  with  the  styloid  process  on 
each  side  by  means  of  a ligament. 

The  uses  of  this  bone  are  to  support  the 
tongue,  and  afford  attachment  to  a great  num- 
ber of  muscles ; some  of  which  perform  the 
motions  of  the  tongue,  while  others  act  on 
the  larynx  and  fauces. 


Sect.  III.  Of  the  Bones  of  the  Trunk. 

T he  trunk  of  the  skeleton  consists  of  the 
spine,  the  thorax,  and  the  pelvis. 

1.  Of  the  Spine. 

The  spine  is  composed  of  a great  number 
of  bones  called  vertebra,  forming  a long  bo- 
ny column,  in  figure  not  much  unlike  the  let- 
ter f This  column,  which  extends  from  the 


100 


Osteology. 


head  to  the  lower  part  of  the  body,  may  be 
said  to  consist  of  two  irregular  and  unequal 
pyramids,  united  to  each  other  in  that  part  of 
the  loins  where  the  last  lumbar  vertebra  joins 
the  os  sacrum. 

The  vertebras  of  the  upper  and  longest  py- 
ramid are  called  true  vertebra , in  contradis- 
tinction to  those  of  the  lowermost  pyramid, 
which,  from  their  being  immoveable  in  the 
adult,  are  styled  f Jse  vertebra.  It  is  upon 
the  bones  of  the  spine  that  the  body  turns  ; 
and  it  is  to  this  circumstance  they  owe  their 
name,  which  is  derived  from  ihe  Latin  verb 
vertere , to  turn. 

The  true  vertebras  are  divided  into  three 
classes  of  cervical,  dorsal  and  lumbar  verte- 
bras.— The  false  vertebrae  consist  of  the  os  sa- 
crum and  os  coccygis. 

In  each  vertebra,  as  in  other  bones,  it  will 
be  necessary  to  remark  the  body  of  the  bone, 
its  processes,  and  cavities. 

The'  body,  which  is  convex  before,  and 
concave  behind,  where  it  assists  in  forming 
the  cavity  of  the  spine,  may  be  compared 
to  part  of  a cylinder  cut  off  transversely. 

Each  vertebra  affords  seven  processes. 
The  first  is  at  the  back  part  of  the  vertebra, 
and  from  its  shape  and  direction  is  named  the 
spinous  process.  On  each  side  of  this  are  two 
others,  which,  from  their  situation  with  re- 
spect to  the  spine,  are  called  transverse  pro- 
cesses. The  four  others  are  styled  oblique  or 
articular  processes.  They  are  much  smaller 
than  the  spinous  or  transverse  ones.  Two  of 


Osteology. 


101 


them  are  placed  on  the  upper,  and  two  on  the 
lower  part  of  each  vertebra,  rising  from  near 
the  basis  of  each  transverse  process.  They 
have  gotten  the  name  of  oblique  processes,  from 
their  situation  with  respect  to  the  processes 
with  which  they  are  articulated  ; and  they  are 
sometimes  styled  articular  processes , from  the 
manner  in  which  they  are  articulated  with 
each  other;  the  two  superior  processes  of  one 
vertebra  being  articulated  with  the  two  infe- 
rior processes  of  the  vertebra  above  it.  Each 
of  these  processes  is  covered  with  cartilage 
at  its  articulation,  and  their  articulations  with 
each  other  are  by  a species  of  ginglimus. 

In  each  vertebra,  between  its  body  and  its 
processes,  we  find  a hole  large  enough  to  ad- 
mit a finger.  These  holes  or  foramina,  corre- 
spond with  each  other  through  all  the  vertebrae, 
and  form  the  long  bony  channel  in  which  the 
spinal  marrow  is  placed.  We  may  likewise 
observe  four  notches  m each  vertebra.  Two 
of  tnese  notches  are  at  the  upper,  and  two 
at  the  lower  part  of  the  bone,  between  the 
oblique  processes  and  the  body  of  the  ver- 
tebra. Each  of  these  notches  meeting  with  a 
similar  opening  in  the  vertebra  above  or  be- 
low it,  forms  a foramen  for  the  passage  of 
blood-vessels,  and  of  the  nerves  out  of  the 
spine. 

The  bones  of  the  spine  are  united  toge- 
ther by  means  of  a substance,  which  in  young 
subjects  appears  to  be  of  a ligamentous,  but 
in  adults  more  of  a cartilaginous  nature.  This 
intervertebral  substance,  which  forms  a kind 


102 


Osteology. 


of  partition  between  the  several  vertebras,  is 
thicker  and  more  flexible  between  the  lumbar 
vertebrae  than  in  the  other  parts  of  the  spine,  the 
most  considerable  motions  of  the  trunk  being 
performed  on  those  vertebrae.  This  substance 
being  very  elastic,  the  extension  and  flexion 
of  the  body,  and  its  motion  backwards  and 
forwards,  or  to  either  side,  are  performed  with 
great  facility.  This  elasticity  seems  to  be  the 
reason  why  people  who  have  been  long  stand- 
ing, or  have  carried  a considerable  weight, 
are  found  to  be  shorter  than  when  they  have 
been  long  in  bed.  In  the  two  first  instances 
the  intervertebral  cartilages  (as  they  are  usu- 
ally called)  are  evidently  more  exposed  to 
compression  than  when  we  are  in  bed  in  an 
horizontal  posture. 

In  advanced  life  these  cartilages  become 
shrivelled,  and  of  course  lose  much  of  their 
elasticity.  This  may  serve  to  account  for  the 
decrease  in  stature  and  the  stooping  forward 
which  are  usually  to  be  observed  in  old  peo- 
ple. 

Besides  the  connection  of  the  several  verte- 
brae by  means  of  this  intervertebral  substance, 
there  are  likewise  many  strong  ligaments,  both 
external  and  internal,  which  unite  the  bones 
of  the  spine  to  each  other.  Their  union  is  al- 
so strengthened  by  a variety  of  strong  muscles 
that  cover  and  surround  the  spine. 

The  bones  of  the  spine  are  found  to  dimi- 
nish in  density,  and  to  be  less  firm  in  their 
texture  in  proportion  as  they  increase  in  bulk; 
so  that  the  lowermost  vertebrae,  though  the 


Osteology. 


103 


largest,  are  not  so  heavy  in  proportion  as  the 
upper  ones.  By  this  means  the  size  of  these 
bones  is  increased  without  adding  to  their 
weight : a circumstance  of  no  little  importance 
in  a part  like  the  spine,  which,  besides  flexi- 
bility and  suppleness,  seems  to  require  light- 
ness as  one  of  its  essential  properties. 

In  very  young  children,  each  vertebra  con- 
sists of  three  bony  pieces  united  by  cartilages 
which  afterwards  ossify. 

There  are  seven  vertebrae  of  the  neck — 
they  are  of  a firmer  texture  than  the  other 
bones  of  the  spine.  Their  transverse  process- 
es are  forked  for  the  lodgment  of  muscles, 
and  at  the  bottom  of  each  we  observe  a fora- 
men, through  which  pass  the  cervical  artery 
and  vein.  The  first  and  second  of  these  ver- 
tebrae must  be  described  more  particularly. 
The  first  approaches  almost  to  an  oval  shape 
— On  its  superior  surface  it  has  two  cavities 
which  admit  the  condyles  of  the  occipital 
bone  with  which  it  is  articulated.  This  verte- 
bra, which  is  called  atlas  from  its  supporting 
the  head,  cannot  well  be  described  as  having 
either  body  or  spinous  process,  being  a kind 
of  bony  ring.  Anteriorly,  where  it  is  articu- 
lated to  the  odontoid  process  of  the  second 
vertebra,  it  is  very  thin.  On  its  upper  surface 
it  has  two  cavities  which  admit  the  condyles 
of  the  occipital  bone.  By  this  connection  the 
head  is  allowed  to  move  forwards  and  back- 
wards, but  has  very  little  motion  in  any  other 
direction. 


104 


Osteology. 


The  second  vertebra  has  gotten  the  name  of 
dentatci , from  its  having,  at  its  upper  and  an- 
terior part,  a process  called  the  odontoid  or 
tooth-like  process , which  is  articulated  with  the 
atlas,  to  which  this  second  vertebra  may  be 
said  to  serve  as  an  axis.  This  odontoid  pro- 
cess is  of  a cylindrical  shape,  somewhat  flat- 
tened, however,  anteriorly  and  posteriorly.  At 
its  fore-part  where  it  is  received  by  the  atlas, 
we  may  observe  a smooth,  convex,  articulat- 
ing surface.  It  is  by  means  of  this  articula- 
tion that  the  head  performs  its  rotatory  motion, 
the  atlas  in  that  case  moving  upon  this  odon- 
toid process  as  upon  a pivot.  But  when  this 
motion  is  in  any  considerable  degree,  or,  in 
other  words,  when  the  head  moves  much  ei- 
ther to  the  right  or  left,  all  the  cervical  verte- 
brae seem  to  assist,  otherwise  the  spinal  mar- 
row would  be  in  danger  of  being  divided  trans- 
versely by  the  first  vertebra. 

The  spinous  process  of  each  of  the  cervi- 
cal vertebrae  is  shorter,  and  their  articular  pro- 
cesses more  oblique,  than  in  the  other  bones 
of  the  spine. 

These  12  vertebrae  are  of  a middle  size  be- 
tween those  of  the  neck  and  loins.  At  their 
sides  we  may  observe  two  depressions,  one  at 
the  upper  and  the  other  at  the  lower  part  of 
the  body  of  each  vertebrae;  which  uniting  with 
similar  depressions  in  the  vertebrae  above  and 
below,  form  articulating  surfaces,  covered  with 
cartilages,  for  receiving  the  heads  of  the  ribs; 
and  at  the  fore-part  of  their  transverse  process 


Osteology , 


105 


(excepting  the  two  last)  we  find  an  articulating 
surface  for  receiving  the  tuberosity  of  the  ribs. 

These  five  vertebras  differ  only  from  those 
of  the  back  in  their  being  larger,  and  in  hav- 
ing their  spinous  processes  at  a greater  dis- 
tance from  each  other.  The  most  consider- 
able motions  of  the  trunk  are  made  on  these 
vertebrae;  and  these  motions  could  not  be  per- 
formed with  so  much  ease,  were  the  process- 
es placed  nearer  to  each  other. 

The  os  sacrum,  which  is  composed  of  five 
or  six  pieces  in  young  subjects,  becomes  one 
bone  in  more  advanced  age. 

It  is  nearly  of  a triangular  figure,  its  infe- 
rior portion  being  bent  a little  forwards.  Its 
superior  part  has  two  oblique  processes  which 
are  articulated  with  the  last  of  the  lumbar  ver- 
tebrae ; and  it  has  likewise  commonly  three 
small  spinous  processes,  which  gradually  be- 
come shorter,  so  that  the  lowermost  is  not  so 
long  as  the  second,  nor  the  second  as  the  up- 
permost. Its  transverse  processes  are  formed 
into  one  oblong  process,  which  becomes  gra- 
dually smaller  as  it  descends.  Its  concave  or 
anterior  side  is  usually  smooth,  but  its  poste- 
rior convex  side  has  many  prominences  (the 
most  remarkable  of  which  are  the  spinous  pro- 
cesses just  now  mentioned,)  which  are  filled 
up  and  covered  with  the  muscular  and  tendi- 
nous parts  behind. 

This  bone  has  five  pair  of  holes,  which  af- 
ford a passage  to  blood-vessels,  and  likewise 
to  the  nerves  that  are  derived  from  the  spinal 
marrow,  which  is  continued  even  here,  being 

O 


106 


Osteology. 


lodged  in  a triangular  cavity,  that  becomes 
smaller  as  it  descends,  and  at  length  termi- 
nates obliquely  at  the  lower  part  of  this  bone. 
Below  the  third  division  of  the  os  sacrum,  this 
canal  is  not  completely  bony  as  in  the  rest  of 
the  spine,  being  secured  at  its  back  part  only 
by  a very  strong  membrane,  so  that  a wound 
at  this  part  must  be  extremely  dangerous. 

The  os  sacrum  is  united  laterally  to  the  os- 
sa innominata  or  hip-bones,  and  below  to  the 
coccyx. 

The  coccyx,  which,  like  the  os  sacrum,  is  / 
in  young  people  made  up  of  three  or  four  dis- 
tinct parts,  usually  becomes  one  bone  in  the 
adult  state. 

It  serves  to  support  the  intestinum  rectum ; 
and,  by  its  being  capable  of  some  degree  of 
motion  at  its  articulation  with  the  sacrum,  and 
being  like  that  bone  bent  forwards,  we  are  en- 
abled to  sit  with  ease. 

This  bone  is  nearly  of  a triangular  shape, 
being  broadest  at  its  upper  part,  and  from 
thence  growing  narrower  to  its  apex,  whejre  it 
is  not  bigger  than  the  little  finger. 

It  has  got  its  name  from  its  supposed  re- 
semblance to  a cuckow’s  beak.  It  differs 
greatly  from  the  vertebrae,  being  commonly 
without  any  processes,  and  having  no  cavity 
for  the  spinal  marrow,  or  foramina  for  the 
transmission  of  nerves. 

The  spine,  of  which  we  have  now  finished 
the  anatomical  description,  is  destined  for  ma- 
ny great  and  important  uses.  The  medulla 
spinalis  is  lodged  in  its  bony  canal  secure  from 


Osteology. 


107 


external  injury.  It  serves  as  a defence  to  the 
abdominal  and  thoracic  viscera,  and  at  the 
same  time  supports  the  head,  and  gives  a ge- 
neral firmness  to  the  whole  trunk. 

We  have  before  compared  it  to  the  letter  f 
and  its  different  turns  will  be  found  to  render 
it  not  very  unlike  the  figure  of  that  letter. — 
In  the  neck  we  see  it  projecting  somewhat  for- 
ward to  support  the  head,  which  without  this 
assistance  would  require  a great  number  of 
muscles. — Lower  down,  in  the  thorax,  we  find 
it  taking  a curved  direction  backwards,  and  of 
course  increasing  the  cavity  of  the  chest.  Af- 
ter this,  in  the  loins,  it  again  projects  forwards 
in  a direction  with  the  centre  of  gravity,  by 
which  means  we  are  easily  enabled  to  keep  the 
body  in  an  erect  posture,  for  otherwise  we 
should  be  liable  to  fall  forward.  Towards  its 
inferior  extremity,  however,  it  again  recedes 
backward,  and  thus  assists  in  forming  the  pel- 
vis, the  name  given  to  the  cavity  in  which  the 
urinary  bladder,  intestinum  rectum,  and  other 
viscera  are  placed. 

If  this  bony  column  had  been  formed  only 
of  one  piece,  it  would  have  been  much  more 
easily  fractured  than  it  is  now  : and  by  confin- 
ing the  trunk  to  a stiff  situation,  a variety  of 
motions  would  have  been  altogether  prevent- 
ed, which  are  now  performed  with  ease  by  the 
great  number  of  bones  of  which  it  is  compos- 
ed. 

It  is  firm,  and  yet  to  this  firmness  there  is 
added  a perfect  flexibility.  If  it  be  required 
to  carry  a load  upon  the  head,  the  neck  be- 


108 


Osteology. 


comes  stiff  with  the  assistance  of  its  muscles, 
and  accommodates  itself  to  the  load,  as  if  it 
was  composed  only  of  one  bone — In  stooping 
likewise,  or  in  turning  to  either  side,  the  spine 
turns  itself  in  every  direction,  as  if  all  its 
bones  were  separated  from  each  other. 

In  a part  of  the  body,  like  the  spine,  that 
is  made  up  of  so  great  a number  of  bones, 
and  intended  for  such  a variety  of  motion, 
there  must  be  a greater  danger  of  dislocation 
than  fracture ; but  we  shall  find,  that  this  is 
very  wisely  guarded  against  in  every  direction 
by  the  processes  belonging  to  each  vertebra, 
and  by  the  ligaments,  cartilages,  &c.  by  which 
these  bones  are  connected  with  each  other. 

2.  Of  the  Bones  of  the  Thorax. 


The  thorax,  or  chest,  is  composed  of  ma- 
ny bones,  viz.  the  sternum  which  is  placed  at 
its  anterior  part,  twelve  ribs  on  each  side 
which  make  up  its  lateral  parts,  and  the  dor- 
sal vertebras  which  constitute  its  posterior  part. 
These  last  have  been  already  described. 

The  sternum  is  the  long  bone  which  ex- 
tends itself  from  the  upper  to  the  lower  part 
of  the  breast  anteriorly,  and  to  which  the  ribs 
and  the  clavicles  are  articulated. 

In  children  it  is  composed  of  several  bones 
united  by  cartilages  ; but  as  we  advance  in  life, 
most  of  these  cartilages  ossify,  and  the  ster- 
num in  the  adult  state  is  found  to  consist  on- 


Osteology. 


109 


ly  of  three  pieces,  and  sometimes  becomes  one 
bone.  It  is  however  generally  described  as 
being  composed  of  three  parts — one  superior, 
which  is  broad,  thick,  and  short ; and  one  in 
the  middle,  which  is  thinner,  narrower,  and 
longer  than  the  other. 

It  terminates  at  its  lower  part  by  a third 
piece,  which  is  called  the  xyphoicl , or  sword- 
like cartilage,  from  its  supposed  resemblance 
to  the  blade  of  a sword,  and  because  in  young 
subjects  it  is  commonly  in  a cartilaginous  state. 

We  have  already  observed,  that  this  bone 
is  articulated  with  the  clavicle  on  each  side. 
It  is  likewise  joined  to  the  fourteen  true  ribs, 
viz.  seven  on  its  right  and  seven  on  its  left 
side. 

The  ribs  are  bones  shaped  like  a bow,  form- 
ing  the  sides  of  the  chest.  There  are  twelve 
on  each  side.  They  are  distinguished  into 
true  and  false  ribs  : The  seven  upper  ribs 
which  are  articulated  to  the  sternum  are  call- 
ed true  ribs , and  the  five  lower  ones  that  are 
not  immediately  attached  to  that  bone  are  call- 
ed false  ribs. 

On  the  inferior  and  interior  surface  of  each 
rib,  we  observe  a sinuosity  for  the  lodgment 
of  an  artery,  vein,  and  nerve. 

The  ribs  are  not  bony  through  their  whole 
length,  their  anterior  part  being  cartilaginous. 
They  are  articulated  with  the  vertebrae  and 
sternum.  Every  rib  (or  at  least  the  greater 
number  of  them)  has  at  its  posterior  part  two 
processes  ; one  at  its  extremity  called  the  head 
of  the  rib,  by  means  of  which  it  is  articulated 


110 


Osteology. 


with  the  body  of  two  vertebrae  ; and  another, 
called  its  tuberosity,  by  which  it  is  articulated 
with  the  transverse  process  of  the  lowest  of 
these  two  vertebra?.  The  first  rib  is  not  arti- 
culated by  its  extremity  to  two  vertebrae,  be- 
ing simply  attached  to  the  upper  part  of  the 
first  vertebra  of  the  back.  The  seven  superi- 
or or  true  ribs  are  articulated  anteriorly  with 
the  sternum  by  their  cartilages  ; but  the  false 
Iribs  are  supported  in  a different  manner — the 
eighth,  which  is  the  first  of  these  ribs,  being 
attached  by  its  cartilage  to  the  seventh  ; the 
ninth  to  the  eighth,  &x. 

The  two  lowermost  ribs  differ  likewise  from 
all  the  rest  in  the  following  particulars : they 
are  articulated  only  with  the  body  of  the  ver- 
tebra, and  not  with  a transverse  process  ; and 
anteriorly,  their  cartilage  is  loose,  not  being 
attached  to  the  cartilages  of  the  other  ribs ; 
and  this  seems  to  be,  because  the  most  consi- 
derable motions  of  the  trunk  are  not  perform- 
ed on  the  lumbar  vertebrae  alone,  but  likewise 
on  the  two  last  vertebrae  of  the  back  ; so  that 
if  these  two  ribs  had  been  confined  at  the  fore 
part  like  the  other  ribs,  and  had  been  likewise 
articulated  with  the  bodies  of  two  vertebrae, 
and  with  the  transverse  processes,  the  moti- 
on of  the  two  last  vertebra,  and  consequently 
of  the  whole  trunk,  would  have  been  impeded. 

The  ribs  help  to  form  the  cavity  of  the  tho- 
rax ; they  afford  attachment  to  different  mus- 
cles ; they  are  useful  in  respiration ; and  they 
serve  as  a security  to  the  heart  and  lungs. 


Osteology . XU 

3.  0/*  the  Bones  of  the  Pelvis. 

The  pelvis  is  composed  of  the  os  sacrum, 
os  coccygis,  and  two  ossa  innominata.  The 
two  first  of  these  bones  were  included  in  the 
account  of  the  spine,  to  which  they  more  pro- 
perly belong. 

In  children,  each  os  innominatum  is  com- 
posed of  three  distinct  bones ; but  as  we  ad- 
vance in  life  the  intermediate  cartilages  gradu- 
ally ossify,  and  the  marks  of  the  original  se- 
paration disappear,  so  that  they  become  one 
irregular  bone  ; still  however  continuing  to  re- 
tain the  names  of  ilium,  ischium,  and  pubis, 
by  which  their  divisions  were  originally  dis- 
tinguished, and  to  be  described  as  three  dif- 
ferent bones  by  the  generality  of  anatomists. 
The  os  ilium  forms  the  upper  and  most  consi- 
derable part  of  the  bone,  the  os  ischium  its 
lower  and  posterior  portion,  and  the  os  pubis 
its  fore  part. 

The  os  ilium  or  haunch  bone,  is  articulated 
posteriorly  to  the  os  sacrum  by  a firm  cartila- 
ginous substance,  and  is  united  to  the  os  pu- 
bis before  and  to  the  os  ischium  below.  Its 
superior  poruon  is  thin,  and  terminates  in  a 
ridge  called  the  crista  or  spine  of  the  ilium, 
and  more  commonly  known  by  the  name  of  the 
haunch.  This  crista  rises  up  like  an  arch  ; 
being  turned  somewhat  outwards,  so  as  to  re- 
semble the  wings  of  a phaeton. 

Externally  this  bone  is  unequally  prominent 
and  hollowed  for  the  lodgment  of  muscles;  in- 
ternally  we  find  it  smooth  and  concave.  At 


112 


Osteology . 


its  lower  part  there  is  a considerable  ridge  on 
its  inner  surface.  This  ridge  extends  from 
the  os  sacrum,  and  corresponds  with  a similar 
prominence  both  on  that  bone  and  the  ischi- 
um ; forms  with  the  inner  part  of  the  ossa  pu- 
bis what  in  midwifery  is  termed  the  brim  of 
the  pelvis. 

The  crista  or  spine,  which  at  first  is  an  epi- 
physis, has  two  considerable  tuberosities ; one 
anteriorly,  and  the  other  posteriorly,  which  is 
the  largest  of  the  two  : these,  from  their  pro- 
jecting more  than  the  parts  of  the  bone  below 
them,  have  gotten  the  name  of  spinal  process- 
es. From  the  anterior  spinous  process,  the 
sartorius  and  tensor  vaginae  femoris  muscles 
have  their  origin ; and  below  the  posterior 
process  we  observe  a considerable  niche  in 
the  bone,  which,  in  the  recent  subject,  is 
formed  into  a large  foramen,  by  means  of  a 
strong  ligament  that  is  stretched  over  its  low- 
er part  from  the  os  sacrum  to  the  sharp-point- 
ed process  of  the  ischium.  This  hole  affords 
a passage  to  the  great  sciatic  nerve,  and  to  the 
posterior  crural  vessels  under  the  pyriform 
muscle,  part  of  which  likewise  passes  out 
here. 

The  os  ischium,  or  hip-bone,  which  is  of 
a very  irregular  figure,  constitutes  the  lower 
lateral  parts  of  the  pelvis,  and  is  commonly 
divided  into  its  body,  tuberosity,  and  ramus. 
The  body  forms  the  lower  and  most  consider- 
able portion  of  the  acetabulum,  and  sends  a 
sharp-pointed  process  backwards,  called  the 
spine  of  the  ischium.  To  this  process  the  li- 


Osteology. 


113 


gament  adheres,  which  was  just  now  spoken 
of,  as  forming  a foramen  for  the  passage  of 
the  sciatic  nerve. — The  tuberosity,  which  is 
the  lowest  part  of  the  trunk,  and  supports  us 
when  we  sit,  is  large  and  irregular,  affording 
origin  to  several  muscles.  From  this  tubero- 
sity we  find  the  bone  becoming  thinner  and 
narrower.  This  part,  which  has  the  name  of 
ramus  or  branch,  passes  forwards  and  up- 
wards, and  concurs  with  the  ramus  of  the  os 
pubis,  to  form  a large  hole  called  the  foramen 
magnum  ischii , or  thyroideum , as  it  is  some- 
times named,  from  its  resemblance  to  a door 
or  shield.  This  hole,  which  in  the  recent 
subject  is  closed  by  a strong  membrane  called 
the  obturator  ligament,  affords  through  its 
whole  circumference  attachment  to  muscles. 
At  its  upper  part  where  we  observe  a niche 
in  the  bone,  it  gives  passage  to  the  obturator 
vessels  and  nerves,  which  go  to  the  inner  part 
of  the  thigh.  Nature  seems  every  where  to 
avoid  an  unnecessary  weight  of  bone,  and 
this  foramen,  no  doubt,  serves  to  lighten  the 
bones  of  the  pelvis. 

The  os  pubis  or  share-bone,  which  with  its 
fellow  forms  the  fore-part  of  the  pelvis,  is  the 
smallest  division  of  the  os  innominatum.  It 
is  united  to  its  fellow  by  means  of  a strong 
cartilage,  which  forms  what  is  called  the  sym- 
physis pubis. 

In  each  os  pubis  we  may  distinguish  the 
body  of  the  bone,  its  angle,  and  ramus.  The 
body  or  outer  part  is  united  to  the  os  ilium. 
The  angle  comes  forward  to  form  the  sym- 

P 


114 


Osteology. 


physis,  and  the  ramus  is  a thin  process  which 
unites  with  the  ramus  of  the  ischium,  to  form 
the  foramen  thyroideum. 

The  three  bones  we  have  described  as  com- 
posing each  os  innominatum,  all  assist  in  form- 
ing the  acetabulum,  in  which  the  head  of  the 
os  femoris  is  received. 

This  cavity  is  every  where  lined  with  a 
smooth  cartilage,  excepting  at  its  inner  part, 
where  we  may  observe  a little  fossa,  in  which 
are  lodged  the  mucilaginous  glands  of  the  joint. 
We  may  likewise  notice  the  pit  or  depression 
made  by  the  round  ligament,  as  it  is  improper- 
ly called,  which,  by  adhering  to  this  cavity  and 
Jto  the  head  of  the  thigh-bone,  helps  to  secure 
the  latter  in  the  socket. 

These  bones,  which  are  united  to  each 
other  and  to  the  spine  by  many  very  strong 
ligaments,  serve  to  support  the  trunk,  and  to 
connect  it  with  the  lower  extremities  ; and  at 
the  same  time  to  form  the  pelvis  or  bason,  in 
which  are  lodged  the  intestines  and  urinary 
bladder,  and  in  women  the  uterus  ; so  that  the 
study  of  this  part  of  osteology  is  of  the  utmost 
importance  in  midwifery. 

It  is  worthy  of  observation,  that  in  women 
the  os  sacrum  is  usually  shorter,  broader,  and 
more  hollowed,  the  ossa  ilia  more  expanded, 
and  the  inferior  opening  of  the  pelvis  larger 
than  in  men. 

Sect.  IV.  Of  the  Extremities. 

These  parts  of  the  skeleton  consist  of  the 
upper  extremity  and  the  lower. 


Osteology, 


115 


1.  Of  the  Upper  Extremity. 


This  consists  of  the  shoulder,  the  arm,  and. 
the  hand. 


1.  Of  the  shoulder. 

The  shoulder  consists  of  two  bones,  the 
clavicula  and  the  scapula. 

The  former,  which  is  so  named  from  its  re* 
semblance  to  the  key  in  use  amongst  the  an- 
cients, is  a little  curved  at  both  its  extremities 
like  an  italic  f It  is  likewise  called  jugulum , 
or  collar-bone,  from  its  situation.  It  is  about 
the  size  of  the  little  finger,  but  longer,  and  be- 
ing of  a very  spongy  substance  is  very  liable 
to  be  fractured.  In  this,  as  in  other  long  bones, 
we  may  distinguish  a body  and  two  extremi- 
ties. The  body  is  rather  flattened  than  round- 
ed. The  anterior  extremity  is  formed  into 
a slightly  convex  head,  which  is  nearly  of  a tri- 
angular shape.  The  inferior  surface  of  the 
head  is  articulated  with  the  sternum.  The 
posterior  extremity,  which  is  flatter  and  broad- 
er than  the  other,  is  connected  to  a process 
of  the  scapula,  called  acromion.  Both  these 
articulations  are  secured  by  ligaments,  and  in 
that  with  the  sternum  we  meet  with  a move- 
able  cartilage,  to  prevent  any  injury  from  fric- 
tion. 

The  clavicle  serves  to  regulate  the  motions 
of  the  scapula,  by  preventing  it  from  being 


116 


Osteology. 


brought  too  much  forwards,  or  carried  too  far 
backwards.  It  affords  origin  to  several  mus- 
cles, and  helps  to  cover  and  protect  the  sub- 
clavian vessels,  which  derive  their  name  from 
their  situation  under  this  bone. 

The  scapula,  or  shoulder-blade,  which  is 
nearly  of  a triangular  shape,  is  fixed  to  the 
posterior  part  of  the  true  ribs,  somewhat  in 
the  manner  of  a buckler.  It  is  of  a very  un- 
equal thickness,  and,  like  all  other  broad,  flat 
bones,  is  somewhat  cellular.  Exteriorly  it  is 
convex,  and  interiorly  concave,  to  accommo- 
date itself  to  the  convexity  of  the  ribs.  We 
observe  in  this  bone  three  unequal  sides,  which 
are  thicker  and  stronger  than  the  body  of  the 
bone,  and  are  therefore  termed  its  costce.  The 
largest  of  the  three,  called  also  the  basis,  is 
turned  towards  the  vertebrae.  Another,  which 
is  less  than  the  former,  is  below  this  ; and  the 
third,  which  is  the  least  of  the  three,  is  at 
the  upper  part  of  the  bone.  Externally  the 
bone  is  elevated  into  a considerable  spine, 
which  rising  small  at  the  basis  of  the  scapula, 
becomes  gradually  higher  and  broader,  and 
divides  the  outer  surface  of  the  bone  into  two 
fossae.  The  superior  of  these,  which  is  the 
smallest,  serves  to  lodge  the  supra  spinatus 
muscle  ; and  the  inferior  fossa,  which  is  much 
larger  than  the  other,  gives  origin  to  the  infra 
spinatus.  This  spine  terminates  in  a broad  and 
flat  process  at  the  top  of  the  shoulder,  called 
the  processus  acromion , to  which  the  clavicle  is 
articulated.  This  process  is  hollowed  at  its 
lower  part  to  allow  a passage  to  the  supra  and 


Osteology. 


117 


infra  spinati  muscles.  The  scapula  has  like- 
wise another  considerable  process  at  its  upper 
part,  which,  from  its  resemblance  to  the  beak 
of  a bird,  is  called  the  coracoid  process.  From 
the  outer  side  of  this  coracoid  process,  a strong 
ligament  passes  to  the  processus  acromion, 
which  prevents  a luxation  of  the  os  humeri  up- 
wards. A third  process  begins  by  a narrow 
neck,  and  ends  in  a cavity  called  glenoid , for 
the  connection  of  the  os  humeri. 

The  scapula  is  articulated  with  the  clavicle 
and  os  humeri,  to  which  last  it  serves  as  a ful- 
crum ; and  by  varying  its  position  it  affords  a 
greater  scope  to  the  bones  of  the  arm  in  their 
different  motions.  It  likewise  gives  origin  to 
several  muscles,  and  posteriorly  serves  as  a de- 
fence to  the  trunk. 

2.  Bones  of  the  Arm. 

The  arm  is  commonly  divided  into  two  parts, 
which  are  articulated  to  each  other  at  the  el- 
bow. The  upper  part  retains  the  name  of  arm, 
properly  so  called,  and  the  lower  part  is  usu- 
ally called  the  fore-arm. 

The  arm  is  composed  of  a single  bone  call- 
ed os  humeri.  This  bone,  which  is  almost  of 
a cylindrical  shape,  may  be  divided  into  its  bo- 
dy and  its  extremities. 

The  upper  extremity  begins  by  a large, 
round  smooth  head,  which  is  admitted  into  the 
glenoid  cavity  of  the  scapula.  On  the  upper 
and  fore  part  of  the  bone  there  is  a groove 
for  lodging  the  long  head  of  the  biceps  mus- 


118 


Osteology . 


cle  of  the  arm  ; and  on  each  side  of  the  groove, 
at  the  upper  end  of  the  bone,  there  is  a tuber- 
cle to  which  the  spinata  muscles  are  fixed. 

The  lower  extremity  has  several  processes 
and  cavities.  The  principal  processes  are  its 
two  condyles,  one  exterior  and  the  other  inte- 
rior, and  of  these  the  last  is  the  largest.  Be- 
tween these  two  we  observe  two  lateral  protu- 
berances, which,  together  with  a middle  cavi- 
ty, form  as  it  were  a kind  of  pully  upon  which 
the  motions  of  the  fore-arm  are  chiefly  per- 
formed At  each  side  of  the  condyles,  as  well 
exteriorly  as  interiorly,  there  is  another  emi- 
nence which  gives  origin  to  several  muscles  of 
the  hand  and  fingers.  Posteriorly  and  superi- 
orly, speaking  with  respect  to  the  condyles,  we 
observe  a deep  fossa  which  receives  a consi- 
derable process  of  the  ulna  ; and  anteriorly  and 
opposite  to  this  fossa,  we  observe  another, 
which  is  much  less  and  receives  another  pro- 
cess of  the  same  bone. 

The  body  of  the  bone  has  at  its  upper  and 
anterior  part  a furrow  which  begins  from  be- 
hind the  head  of  the  bone,  and  serves  to  lodge 
the  tendon  of  a muscle.  The  body  of  the  os 
humeri  is  hollow  through  its  whole  length,  and, 
like  all  other  long  bones,  has  its  marrow. 

This  bone  is  articulated  at  its  upper  part  to 
the  scapula.  This  articulation,  which  allows 
motion  every  way,  is  surrounded  by  a capsu- 
lar ligament ; that  is  sometimes  torn  in  luxa- 
tion, and  becomes  an  obstacle  to  the  easy  re- 
duction of  the  bone.  Its  lower  extremity  is 
articulated  with  the  bones  of  the  fore-arm. 


Osteology.  119 

The  fore-arm  is  composed  of  two  bones,  the 
ulna  and  radius. 

The  ulna  or  elbow-bone  is  much  less  than 
the  os  humeri,  and  becomes  gradually  small- 
er as  it  descends  to  the  wrist.  At  its  upper 
part  it  has  two  processes  and  two  cavities.  Of 
the  two  processes,  the  largest,  which  is  situ-* 
ated  posteriorly,  and  called  the  olecranon , is 
admitted  into  the  posterior  fossa  of  the  os  hu- 
meri. The  other  process  is  placed  anteriorly, 
and  is  called  the  coronoid  process.  In  bending 
the  arm  it  enters  into  the  anterior  fossa  of  the 
os  humeri.  This  process  being  much  smaller 
than  the  other,  permits  the  fore-arm  to  bend 
inwards ; whereas  the  olecranon,  which  is 
shaped  like  a hook,  reaches  the  bottom  of  its 
fossa  in  the  os  humeri  as  soon  as  the  arm  be- 
comes straight,  and  will  not  permit  the  fore- 
arm to  be  bent  backwards.  The  ligaments 
likewise  oppose  this  motion. 

Between  the  two  processes  we  have  describ- 
ed, there  is  a considerable  cavity  called  the 
sygmoid  cavity,  divided  into  two  fossae  by  a 
small  eminence,  which  passes  from  one  pro- 
cess to  the  other  ; it  is  by  means  of  this  cavity 
and  the  two  processes,  that  the  ulna  is  articu- 
lated with  the  os  humeri  by  ginglimus. 

At  the  bottom  of  the  coronoid  process  interi- 
orly, there  is  a small  sygmoid  cavity,  which 
serves  for  the  articulation  of  the  ulna  with  the 
radius. 

The  body  of  the  ulna  is  of  a triangular 
shape : Its  lower  extremity  terminates  by  a 
small  head  and  a little  styloid  process.  The 


Osteology. 


12® 

ulna  is  articulated  above  to  the  os  humeri — 
both  above  and  below  to  the  radius,  and  to 
the  wrist  at  its  lower  extremity.  All  these  ar- 
ticulations are  secured  by  means  of  ligaments. 
The  chief  use  of  this  bone  seems  to  be  to  sup- 
port and  regulate  the  motions  of  the  radius. 

The  radius,  which  is  so  named  from  its  sup- 
posed resemblance  to  the  spoke  of  a wheel,  is 
placed  at  the  inside  of  the  fore-arm.  It  is 
somewhat  larger  than  the  ulna,  but  not  quite 
so  long  as  that  bone.  Its  upper  part  is  cylin- 
drical, hollowed  superiorly  to  receive  the  out- 
er condyle  of  the  os  humeri.  Laterally  it  is 
admitted  into  the  little  sygmoid  cavity  of  the 
ulna,  and  the  cylindrical  part  of  the  bone  turns 
in  this  cavity  in  the  motions  of  pronation  and 
supination.*  This  bone  follows  the  ulna  in 
flexion  and  extension,  and  may  likewise  be 
moved  round  its  axis  in  any  direction.  The 
lower  extremity  of  the  radius  is  much  larger 
and  stronger  than  its  upper  part ; the  ulna,  on 
the  contrary,  is  smaller  and  weaker  below  than 
above  ; so  that  they  serve  to  supply  each  other’s 
deficiencies  in  both  those  parts. 

On  the  external  side  of  this  bone,  we  ob- 
serve a small  cavity  which  is  destined  to  re- 
ceive the  lower  end  of  the  ulna ; and  its  low- 
er extremity  is  formed  into  a large  cavity,  by 
means  of  which  it  is  articulated  with  the  bones 

* The  motions  of  pronation  and  supination  may  be  easily 
described.  If  the  palm  of  the  hand,  for  instance,  is  placed  on 
the  surface  of  a table,  the  hand  may  be  said  to  be  in  a state  of 
pronation ; but  if  the  back  part  of  the  hand  is  turned  towards 
the  table,  the  hand  will  be  then  in  a state  of  supination. 


Osteology. 


121 


of  the  wrist,  and  on  this  account  it  is  some- 
times called  manubrium  manus.  It  supports 
the  two  first  bones  of  the  wrist  on  the  side  of 
the  thumb,  whereas  the  ulna  is  articulated  with 
that  bone  of  the  wrist  which  corresponds  with 
the  little  finger. 

Through  the  whole  length  both  of  this  bone 
and  the  ulna,  a ridge  is  observed,  which  affords 
attachment  to  an  interosseous  ligament.  This 
ligament  fills  up  the  space  between  the  two 
bones. 


3.  Bones  of  the  Hand. 

The  carpus  or  wrist  consists  of  eight  small 
bones  of  an  irregular  shape,  and  disposed  in  two 
unequal  rows.  Those  of  the  upper  row  are 
articulated  with  the  bones  of  the  fore-arm,  and 
those  of  the  lower  one  with  the  metacarpus. 

The  ancient  anatomists  described  these 
bones  numerically ; Lyserus  seems  to  have 
been  the  first  who  gave  to  each  of  them  a par- 
ticular name.  The  names  he  adopted  are 
founded  on  the  figure  of  the  bones,  and  are 
now  pretty  generally  received,  except  the  first, 
which  instead  of  (the  name  given  to  it 

by  Lyserus,  on  account  of  its  sinus  that  ad- 
mits a part  of  the  os  magnum),  has  by  later 
writers  been  named  Scaphoides  or  Naviculare. 
This,  which  is  the  outermost  of  the  upper  row 
(considering  the  thumb  as  the  outer  side  of 
the  hand),  is  articulated  with  the  radius ; on 
its  inner  side  it  is  connected  with  the  os  lu- 
nare,  and  below  to  the  trapezium  and  trape- 

Q 


122 


Osteology. 


zoides.  Next  to  this  is  a smaller  bone,  called 
the  os  lunar e : because  its  outer  side,  which 
is  connected  with  the  scaphoides,  is  shaped 
like  a crescent.  This  is  likewise  articulated 
with  the  radius.  On  its  inner  side  it  joins  the 
os  cuneiforme,  and  anteriorly,  the  os  magnum 
and  os  unciforme. 

The  os  cuneiforme,  which  is  the  third  bone 
in  the  upper  row,  is  compared  to  a wedge, 
from  its  being  broader  above,  at  the  back  of 
the  hand,  than  it  is  below.  Posteriorly  it  is 
articulated  with  the  ulna,  and  anteriorly  with 
the  os  unciforme. 

These  three  bones  form  an  oblong  articulat- 
ing surface,  covered  by  cartilage,  by  which 
the  hand  is  connected  with  the  fore-arm. 

The  os  pisiforme,  or  pea-like  bone,  which 
is  smaller  than  the  three  just  now  described, 
though  generally  classed  with  the  bones  of  the 
upper  row,  does  not  properly  belong  to  either 
series,  being  placed  on  the  under  surface  of 
the  os  cuneiforme,  so  as  to  project  into  the 
palm  of  the  hand.  The  four  bones  of  the  se- 
cond row  correspond  with  the  bones  of  the 
thumb  and  fingers ; the  first,  second,  and 
fourth,  are  from  their  shapes  named  trapezi- 
um., trapezoides , and  unciforme ; the  third,  from 
its  being  the  largest  bone  of  the  carpus,  is  styl- 
ed os  magnum. 

All  these  bones  are  convex  towards  the  back, 
and  slightly  concave  towards  the  palm  of  the 
hand  ; their  articulating  surfaces  are  covered 
with  cartilages,  and  secured  by  many  strong 
ligaments,  particularly  by  two  ligamentous  ex- 


Osteology. 


123 


pansions,  called  the  external  and  internal  an- 
nular ligaments  of  the  wrist.  The  former  ex- 
tends in  an  oblique  direction  from  the  os  pisi- 
forme  to  the  styloid  process  of  the  radius,  and 
is  an  inch  and  an  half  in  breadth ; the  latter  or 
internal  annular  ligament  is  stretched  from  the 
os  pisiforme  and  os  unciforme,  to  the  os  sca- 
phoides  and  trapezium.  These  annular  liga- 
ments likewise  serve  to  bind  down  the  tendons 
of  the  wrist  and  fingers. 

The  metacarpus  consists  of  four  bones, 
which  support  the  fingers  ; externally  they  are 
a little  convex,  and  internally  somewhat  con- 
cave, where  they  form  the  palm  of  the  hand. 
They  are  hollow  and  of  a cylindrical  shape. 

At  each  extremity  they  are  a little  hollow- 
ed for  their  articulation  ; superiorly  with  the 
bones  of  the  carpus,  and  inferiorly  with  the 
first  phalanx  of  the  fingers,  in  the  same  man- 
ner as  the  several  phalanges  of  the  fingers 
are  articulated  with  each  other. 

The  five  fingers  of  each  hand  are  composed 
of  fifteen  bones,  disposed  in  three  ranks  call- 
ed phalanges : the  bones  of  the  first  phalanx, 
which  are  articulated  with  the  metacarpus,  are 
the  largest,  and  those  ef  the  last  phalanx  the 
smallest.  All  these  bones  are  larger  at  their 
extremities  than  in  their  middle  part. 

We  observe  at  the  extremities  of  the  bones 
of  the  carpus,  metacarpus,  and  fingers,  seve- 
ral inequalities  that  serve  for  their  articulation 
with  each  other ; and  these  articulations  are 
strengthened  by  means  of  the  ligaments  which 
surround  them. 


124 


Osteology . 


It  will  be  easily  understood  that  this  multi- 
plicity  of  bones  in  the  hand  (for  there  are  27 
in  each  hand)  is  essential  to  the  different  mo- 
tions we  wish  to  perform.  If  each  finger  was 
composed  only  of  one  bone  instead  of*  three, 
it  would  be  impossible  for  us  to  grasp  any 
thing. 

2.  Of  the  Lower  Extremities. 

Each  lower  extremity  is  divided  into  four 
parts,  viz.  the  os  femoris,  or  thigh  bone : the 
rotula,  or  knee  pan ; the  leg  and  the  foot. 

1.  Of  the  Thigh. 

The  thigh  is  composed  only  of  this  bone, 
which  is  the  largest  and  strongest  we  have. 
It  will  be  necessary  to  distinguish  its  body  and 
extremities : its  body,  which  is  of  a cylindri- 
cal shape,  is  convex  before  and  concave  be- 
hind, where  it  serves  to  lodge  several  muscles. 

Throughout  two-thirds  of  its  length  we  ob- 
serve a ridge  called  lined  aspera , which  origi- 
nates from  the  trochanters,  and  after  running 
for  some  way  downwards,  divides  into  two 
branches,  that  terminate  in  the  tuberosities  at 
the  lower  extremity  of  the  bone. 

At  its  upper  extremity  we  must  describe  the 
neck  and  smooth  head  of  the  bone,  and  like- 
wise two  considerable  processes:  the  head, 
which  forms  the  greater  portion  of  a sphere 
unequally  divided,  is  turned  inwards,  and  re- 
ceived into  the  great  cotyloid  cavity  of  the  os 


Osteology. 


125 


innominatum.  At  this  part  of  the  bone  there  is  a 
little  fossa  to  be  observed,  to  which  the  round 
ligament  is  attached,  and  which  we  have  al- 
ready described  as  tending  to  secure  the  head 
of  this  bone  in  the  great  acetabulum*  The 
neck  is  almost  horizontal,  considered  with  re- 
spect to  its  situation  with  the  body  of  the  bone. 
Of  the  two  processes,  the  external  one,  which 
is  the  largest,  is  called  trochanter  major ; and 
the  other,  which  is  placed  on  the  inside  of  the 
bone,  trochanter  minor.  They  both  afford  at- 
tachment to  muscles.  The  articulation  of  the 
os  femoris  with  the  trunk  is  strengthened  by 
means  of  a capsular  ligament,  which  adheres 
every  where  round  the  edge  of  the  great  co- 
tyloid cavity  of  the  os  innominatum,  and  sur- 
rounds the  head  of  the  bone. 

The  os  femoris  moves  upon  the  trunk  in 
every  direction. 

At  the  lower  extremity  of  the  bone  are  two 
processes  called  the  condyles,  and  an  interme- 
diate smooth  cavity,  by  means  of  which  it  is 
articulated  with  the  leg  by  ginglimus. 

All  round  the  under  end  of  the  bone  there 
is  an  irregular  surface  where  the  capsular  li- 
gament of  the  joint  has  its  origin,  and  where 
blood-vessels  go  into  the  substance  of  the 
bone. 

Between  the  condyles  there  is  a cavity  pos- 
teriorly, in  which  the  blood-vessels  and  nerves 
are  placed,  secure  from  the  compression  to 
which  they  would  otherwise  be  exposed  in 
the  action  of  bending  the  leg,  and  which  would 
not  fail  to  be  hurtful. 


126 


Osteology. 


At  the  side  of  each  condyle  externally,  there 
is  a tuberosity,  from  whence  the  lateral  liga- 
ments originate,  which  are  extended  down  to 
the  tibia. 

A ligament  likewise  arises  from  each  con- 
dyle posteriorly.  One  of  these  ligaments 
passes  from  the  right  to  the  left,  and  the  other 
from  the  left  to  the  right,  so  that  they  inter- 
sect each  other,  and  for  that  reason  are  called 
the  cross  ligaments. 

The  lateral  ligaments  prevent  the  motion  of 
the  leg  upon  the  thigh  to  the  right  or  left ; and 
the  cross  ligaments,  which  are  also  attached 
to  the  tibia,  prevent  the  latter  from  being 
brought  forwards. 

In  new-born  children  all  the  processes  of 
this  bone  are  cartilaginous. 

2.  The  Rotula,  or  Knee-pan. 

The  rotula,  patella,  or  knee-pan,  as  it  is 
differently  called,  is  a flat  bone  about  four  or 
five  inches  in  circumference,  and  is  placed  at 
the  fore-part  of  the  joint  of  the  knee.  In  its 
shape  it  is  somewhat  like  the  common  figure 
of  the  heart,  with  its  point  downwards. 

It  is  thinner  at  its  edge  than  in  its  middle 
part ; at  its  fore-part  it  is  smooth  and  some- 
what convex ; its  posterior  surface,  which  is 
more  unequal,  affords  an  elevation  in  the  mid- 
dle which  is  admitted  between  the  two  con- 
dyles of  the  os  femoris. 

This  bone  is  retained  in  its  proper  situation 
by  a strong  ligament  which  every  where  sur- 


Osteology . 


127 


rounds  it,  and  adheres  both  to  the  tibia  and  os 
femoris ; it  is  likewise  firmly  connected  with 
the  tibia  by  means  of  a strong  tendinous  liga- 
ment of  an  inch  in  breadth,  and  upwards  of 
two  inches  in  length,  which  adheres  to  the 
lower  part  of  the  patella,  and  to  the  tubero- 
sity at  the  upper  end  of  the  tibia.  On  account 
of  this  connection,  it  is  very  properly  consi- 
dered as  an  appendage  to  the  tibia,  which  it 
follows  in  all  its  motions,  so  as  be  to  it  what 
the  olecranon  is  to  the  ulna.  There  is  this 
difference,  however,  that  the  olecranon  is  a 
fixed  process ; whereas  the  patella  is  movea- 
ble, being  capable  of  sliding  from  above  down- 
wards and  from  below  upwards.  This  mobi- 
lity is  essential  to  the  rotatory  motion  of  the 

le&‘ 

In  very  young  children  this  bone  is  entirely 
cartilaginous. 

The  principal  use  of  the  patella  seems  to 
be  to  defend  the  articulation  of  the  knee  from 
external  injury;  it  likewise  tends  to  increase 
the  power  of  the  extensor  muscles  of  the  leg, 
by  removing  their  direction  farther  from  the 
centre  of  motion  in  the  manner  of  a pulley. 

3.  Of  the  Leg. 

The  leg  is  composed  of  two  bones:  of  these 
the  inner  one,  which  is  the  largest,  is  called 
tibia  ; the  other  is  much  smaller,  and  named 
fibula. 

The  tibia,  which  is  so  called  from  its  re- 
semblance to  the  musical  pipe  of  the  ancients, 


128 


Osteology. 


has  three  surfaces,  and  is  not  very  unlike  a 
triangular  prism.  Its  posterior  surface  is  the 
broadest ; anteriorly  it  has  a considerable 
ridge  called  the  shin,  between  which  and  the 
skin  there  are  no  muscles.  At  the  upper  ex- 
tremity of  this  bone  are  two  surfaces,  a little 
concave,  and  separated  from  each  other  by  an 
intermediate  elevation.  The  two  little  cavities 
receive  the  condyles  of  the  os  femoris,  and 
the  eminence  between  them  is  admitted  into 
the  cavity  which  we  spoke  of  as  being  be- 
tween the  two  condyles  ; so  that  this  articula- 
tion affords  a specimen  of  the  complete  gin- 
glimus.  Under  the  external  edge  of  the  up- 
per end  of  this  bone  is  a circular  flat  surface, 
which  receives  the  head  of  the  fibula. 

At  the  lower  and  inner  portion  of  the  tibia, 
we  observe  a considerable  process  called  mal- 
leolus interims.  The  basis  of  the  bone  termi- 
nates in  a large  transverse  cavity,  by  which  it 
is  articulated  with  the  uppermost  bone  of  the 
foot.  It  has  likewise  another  cavity  at  its  low- 
er end  and  outer  side,  which  is  somewhat  ob- 
long, and  receives  the  lower  end  of  the  fibula. 

The  tibia  is  hollow  through  its  whole  length. 

The  fibula  is  a small  long  bone  situated  on 
the  outside  of  the  tibia.  Its  superior  extremi- 
ty does  not  reach  quite  so  high  as  the  upper 
part  of  the  tibia,  but  its  lower  end  descends 
somewhat  lower.  Both  above  and  below,  it 
is  articulated  with  the  tibia  by  means  of  the 
lateral  cavities  we  noticed  in  our  description 
of  that  bone. 


Osteology. 


129 


Its  lower  extremity  is  stretched  out  into  a 
coronoid  process,  which  is  flattened  at  its  in- 
side, and  is  convex  externally,  forming  what 
is  called  the  malleolus  externus  or  outer  ankle . 
This  is  rather  lower  than  the  malleolus  inter- 
nus  of  the  tibia. 

The  body  of  this  bone,  which  is  irregularly 
triangular,  is  a little  hollow  at  its  internal  sur- 
face, which  is  turned  towards  the  tibia ; and  it 
affords  like  that  bone,  through  its  whole  length, 
attachment  to  a ligament,  which  from  its  situa- 
tion is  called  the  interosseous  ligament. 

4.  Of  the  Foot. 

' b')  \ n 

The  foot  consists  of  the  tarsus,  metatarsus, 
and  toes. 

The  tarsus  is  composed  of  seven  bones,  viz. 
the  astragalus,  os  calcis,  os  naviculare,  os  cu- 
boides,  and  three  others  called  cuneiform, 
bones. 

The  astragalus  is  a large  bone  with  which 
both  the  tibia  and  fibula  are  articulated.  It 
is  the  uppermost  bone  of  the  foot ; it  has  se- 
veral surfaces  to  be  considered ; its  upper, 
and  somewhat  posterior  part,  which  is  smooth 
and  convex,  is  admitted  into  the  cavity  of  the 
tibia.  Its  lateral  parts  are  connected  with  the 
malleoli  of  the  two  bones  of  the  leg ; below, 
it  is  articulated  with  the  os  calcis,  and  its  an- 
terior surface  is  received  by  the  os  naviculare. 
All  these  articulations  are  secured  by  means 
of  ligaments. 


R 


130 


Osteology. 


The  os  calcis,  or  calcaneum,  which  is  of  a 
very  irregular  figure,  is  the  largest  bone  of  the 
foot.  Behind,  it  is  formed  into  a considerable 
tuberosity  called  the  heel ; without  this  tube- 
rosity, which  supports  us  in  an  erect  posture, 
and  when  we  walk,  we  should  be  liable  to  fall 
backwards. 

On  the  internal  surface  of  this  bone,  we 
observe  a considerable  sinuosity,  which  affords 
a passage  to  the  tendon  of  a muscle : and  to 
the  posterior  part  of  the  os  calcis,  a strong 
tendinous  cord  called  tendo  achillis*  is  attach- 
ed, which  is  formed  by  the  tendons  of  seve- 
ral muscles  united  together.  The  articulation 
of  this  with  the  other  bones  is  secured  by 
means  of  ligaments. 

The  os  naviculare,  or  scaphoides,  (for  these 
two  terms  have  the  same  signification),  is  so 
called  on  account  of  its  resemblance  to  a little 
bark.  At  its  posterior  part,  which  is  concave, 
it  receives  the  astragalus  ; anteriorly  it  is  ar- 
ticulated with  the  cuneiform  bones,  and  late- 
rally is  connected  with  the  os  cuboides. 

The  os  cuboides  forms  an  irregular  cube. 
Posteriorly  it  is  articulated  with  the  os  calcis  ; 
anteriorly  it  supports  the  two  last  bones  of  the 
metatarsus,  and  laterally  it  joins  the  third  cu- 
neiform bone  and  the  os  naviculare. 

Each  of  the  ossa  cuneiformia,  which  are 
three  in  number,  resembles  a wedge,  and  from 
this  similitude  their  name  is  derived.  They 

* This  tendon  is  sometimes  ruptured  by  jumping,  dancing, 
or  other  violent  efforts. 


Osteology. 


131 


are  placed  next  to  the  metatarsus  by  the  sides 
of  each  other,  and  are  usually  distinguished 
into  os  cuneiforme  externum , medium  or  mini- 
mum ^ and  internum  or  maximum.  The  supe- 
rior surface  of  these  bones,  from  their  wedge- 
like shape,  is  broader  than  that  which  is  be- 
low, where  they  help  to  form  the  sole  of  the 
foot ; posteriorly  they  are  united  to  the  os  na- 
viculare,  and  anteriorly  they  support  the  three 
first  metatarsal  bones. 

When  these  seven  bones  composing  the  tar- 
sus are  viewed  together  in  the  skeleton,  they 
appear  convex  above,  where  they  help  to  form 
the  upper  part  of  the  foot ; and  concave  under- 
neath, where  they  form  the  hollow  of  the  foot, 
in  which  the  vessels,  tendons,  and  nerves  of 
the  foot  are  placed  secure  from  pressure. 

They  are  united  to  each  other  by  very  strong 
ligaments,  and  their  articulation  with  the  foot 
is  secured  by  a capsular  and  two  lateral  liga- 
ments ; each  of  the  latter  is  covered  by  an  an- 
nular ligament  of  considerable  breadth  and 
thickness,  which  serves  to  bind  down  the  ten- 
dons of  the  foot,  and  at  the  same  time  to 
strengthen  the  articulation. 

The  os  cuneiforme  externum  is  joined  late- 
rally to  the  os  cuboides. 

These  bones  complete  our  account  of  the  tar- 
sus. Though  what  we  have  said  of  this  part 
of  the  osteology  has  been  very  simple  and  con- 
cise, yet  many  readers  may  not  clearly  under- 
stand it : but  if  they  will  be  pleased  to  view 
these  bones  in  their  proper  situation  in  the 


132 


Osteology . 


skeleton,  all  that  we  have  said  of  them  will 
be  easily  understood. 

The  metatarsus  is  made  up  of  five  bones^ 
whereas  the  metacarpus  consists  only  of  four. 
The  cause  of  this  difference  is,  that  in  the 
hand  the  last  bone  of  the  thumb  is  not  includ- 
ed among  the  metacarpal  bones ; whereas  in 
the  foot  the  great  toe  has  only  two  bones.  The 
first  of  these  bones  supports  the  great  toe  and 
is  much  larger  than  the  rest,  which  nearly  re- 
semble each  other/in  size. 

These  bones  are  articulated  by  one  extremi- 
ty with  the  cuneiform  bones  and  the  os  cuboi- 
des,  and  by  their  other  end  with  the  toes. 

Each  of  the  toes,  like  the  fingers,  consists  of 
three  bones,  except  the  great  toe,  which  is 
formed  of  two  bones.  Those  of  the  other 
four  are  distinguished  into  three  phalanges. 
Although  the  toes  are  more  confined  in  their 
motion  than  the  fingers,  yet  they  appear  to  be 
perfectly  fitted  for  the  purposes  they  are  de- 
signed for.  In  walking,  the  toes  bring  the 
centre  of  gravity  perpendicular  to  the  advanc- 
ed foot ; and  as  the  soles  of  the  feet  are  natu- 
rally concave,  we  can  at  pleasure  increase  this 
concavity,  and  form  a kind  of  vault,  which 
adjusts  itself  to  the  different  inequalities  that 
occur  to  us  in  walking;  and  which,  without 
this  mode  of  arrangement,  would  incommode 
us  exceedingly,  especially  when  bare-footed. 


Osteology. 


133 


4 . Of  the  Ossa  Sesamoidea. 


Besides  the  bones  we  have  already  de- 
scribed, there  are  several  small  ones  that  are 
met  with  only  in  the  adult  skeleton,  and  in 
persons  who  are  advanced  in  life  ; which,  from 
their  supposed  general  resemblance  to  the 
seeds  of  the  sesamum,  are  called  ossa  sesa- 
moidea. They  are  commonly  to  be  seen  at 
the  first  joint  of  the  great  toe,  and  sometimes 
at  the  joints  of  the  thumb  ; they  are  likewise 
now  and  then  to  be  found  at  the  lower  extremity 
of  the  fibula,  upon  the  condyles  of  the  thigh- 
bone, under  the  os  cuboides  of  the  tarsus,  and 
in  other  parts  of  the  body.  Their  size  and  num- 
ber seem  constantly  to  be  increased  by  age  and 
hard  labour ; and  as  they  are  generally  found 
in  situations  where  tendons  and  ligaments  are 
most  exposed  to  the  action  of  muscles,  they 
are  now  generally  considered  as  ossified  por- 
tions of  ligaments  or  tendons. 

The  upper  surface  of  these  bones  is  usual- 
ly convex,  and  adherent  to  the  tendon  that  co- 
vers it ; the  side  which  is  next  to  the  joint  is 
smooth  and  flat.  Though  their  formation  is 
accidental,  yet  they  seem  to  be  of  some  use, 
by  raising  the  tendons  farther  from  the  centre 
of  motion,  and  consequently  increasing  the 
power  of  the  muscles.  In  the  great  toe  and 
thumb  they  are  likewise  useful,  by  forming  a 
groove  for  the  flexor  tendons. 


134 


Osteology. 


EXPLANATION  OF  THE  PLATES 
OF  OSTEOLOGY. 


Plate.  XIX. 

Fig.  1,  A Front-view  of  the  Male  Skele- 
ton. 

A,  The  os  frontis.  B,  The  os  parietale.  C, 
The  coronal  suture.  D,  The  squamous  part 
of  the  temporal  bones.  E,  The  squamous  su- 
ture. F,  The  zygoma.  G,  The  mastoid  pro- 
cess. H,  The  temporal  process  of  the  sphe- 
noid bone.  I,  The  orbit.  K,  The  os  malae. 
L,  The  os  maxillare  superius.  M,  Its  nasal 
process.  N,  The  ossa  nasi.  O,  The  os  un- 
guis. P,  The  maxilla  inferior.  Q,  The  teeth 
which  are  sixteen  in  number  in  each  jaw.  R, 
The  seven  cervical  vertebrae,  with  their  inter- 
mediate cartilages.  S,  Their  transverse  pro- 
cesses. T,  The  twelve  dorsal  vertebrae,  with 
their  intermediate  cartilages.  U,  The  five 
lumbar  vertebrae.  V,  Their  transverse  pro- 
cesses. W,  The  upper  part  of  the  os  sacrum. 
X,  Its  lateral  parts.  The  holes  seen  on  its 
fore  part  are  the  passages  of  the  undermost 
spinal  nerves  and  small  vessels.  Opposite  to 
the  holes,  the  marks  of  the  original  divisions 
of  the  bone  are  seen.  Y,  The  os  ilium.  Z, 
Its  crest  or  spine,  a,  The  anterior  spinous 
processes,  b,  The  brim  of  the  pelvis.  c? 


Axa to  my 


Osteology.  135 

The  ischiatic  niche,  d,  The  os  ischium,  e, 
Its  tuberosity,  f,  Its  spinous  process,  g,  Its 
crus,  h,  The  foramen  thyroideum.  i,  The 
os  pubis,  k,  The  symphysis  pubis.  1,  The 
crus  pubis,  m,  The  acetabulum,  n,  The  se- 
venth or  last  true  rib*  o,  The  twelfth  or  last 
false  rib.  p,  The  upper  end  of  the  sternum, 
q,  The  middle  piece,  r,  The  under  end,  or 
cartilage  ensiformis.  s,  The  clavicle,  t,  The 
internal  surface  of  the  scapula,  u,  Its  acro- 
mion. v,  Its  coracoid  process,  w,  Its  cervix., 
x,  The  glenoid  cavity,  y,  The  os  humeri,  z. 
Its  head  which  is  connected  to  the  glenoid  ca- 
vity. 1,  Its  external  tubercle.  2,  Its  inter- 
nal tubercle.  3.  The  groove  for  lodging  the 
long  head  of  the  biceps  muscle  of  the  arm. 
4,  The  internal  condyle.  5,  The  external 
condyle.  Between  4 and  5,  the  trochlea.  6, 
The  radius.  7,  Its  head.  8,  Its  tubercle.  9, 
The  ulna-  10,  Its  coronoid  process.  11,  12, 
13,  14,  15,  16,  17,  18,  The  carpus  ; compos- 
ed of  os  naviculare,  os  lunare,  os  cuneifor- 
me,  os  pisiforme,  os  trapezium,  os  trapezoi- 
des,  os  magnum,  os  unciforme.  19,  The  five 
bones  of  the  metacarpus.  20,  The  two  bones 
of  the  thumb.  21,  The  three  bones  of  each 
of  the  fingers.  22,  The  os  femoris.  23,  Its 
head.  24,  Its  cervix.  25,  The  trochanter 
major.  26,  The  trochanter  minor.  27,  The 
internal  condyle.  28,  The  external  condyle 
29,  The  rotula.  30,  The  tibia.  31,  Its  head* 
32,  Its  tubercle.  33,  Its  spine.  34,  The  mal- 
leolus interims.  35,  The  fibula.  36,  Its  head. 
37,  The  malleolus  externus.  The  tarsus  is 


136 


Osteology. 


composed  of,  38,  The  astragalus;  39,  The 
os  calcis  ; 40,  The  os  naviculare ; 41,  Three 
ossa  cuneiformia,  and  the  os  cuboides,  which 
is  not  seen  in  this  figure.  42,  The  five  bones 
of  the  metatarsus.  43,  The  two  bones  of 
the  great  toe.  44,  The  three  bones  of  each 
of  the  small  toes. 

Fig.  2.  A Front-view  of  the  Skull. 

A,  The  os  frontis.  B.  The  lateral  part 
of  the  os  frontis,  which  gives  origin  to  part  of 
the  temporal  muscle.  C,  The  superciliary 
ridge.  D,  The  superciliary  hole  through 
which  the  frontal  vessels  and  nerves  pass.  E 
E,  The  orbitar  processes.  F,  The  middle  of 
the  transverse  suture.  G,  The  upper  part  of 
the  orbit.  H,  The  foramen  opticum.  I,  The 
foramen  lacerum.  K,  The  inferior  orbitar  fis- 
sure. L,  The  os  unguis.  M,  The  ossa  na- 
si. N,  The  os  maxillare  superius.  O,  Its  na- 
sal process.  P,  The  external  orbitar  hole 
through  which  the  superior  maxillary  vessels 
and  nerves  pass.  Q,  The  os  malae.  R,  A 
passage  for  small  vessels  into,  or  out  of,  the 
orbit.  S,  The  under  part  of  the  left  nostril. 
T,  The  septum  narium.  U,  The  os  spongi- 
osum superius.  V,  The  os  spongiosum  infe- 
rius.  W,  The  edge  of  the  alveoli,  or  spongy 
sockets,  for  the  teeth-  X,  The  maxilla  infe- 
rior. Y,  The  passage  for  the  inferior  maxil- 
lary vessels  and  nerves- 


Osteology . 


137 


Fig.  3.  A Side-view  of  the  Skull. 

A,  The  os  frontis.  B,  The  coronal  suture. 
C,  The  os  parietale.  D,  An  arched  ridge 
which  gives  origin  to  the  temporal  muscle.  E, 
The  squamous  suture.  F,  The  squamous 
part  of  the  temporal  bone  ; and,  farther  for- 
wards, the  temporal  process  of  the  sphenoid 
bone.  G,  The  zygomatic  process  of  the  tem- 
poral bone.  H,  The  zygomatic  suture.  I,  The 
mastoid  process  of  the  temporal  bone.  K,  The 
meatus  auditorius  externus-  L,  The  orbitar 
plate  of  the  frontal  bone,  under  which  is  seen 
the  transverse  suture.  M,  The  pars  plana  of 
the  ethmoid  bone.  N,  The  os  unguis.  O, 
The  right  os  nasi.  P,  The  superior  maxilla- 
ry bone.  Q,  Its  nasal  process.  R,  The  two 
dentes  incisores.  S,  The  dens  caninus.  T, 
the  two  small  molares.  U,  The  three  large 
molares.  V,  The  os  malse.  W,  The  lower 
jaw.  X,  Its  angle.  Y,  The  coronoid  process. 
Z,  The  condyloid  process,  by  which  the  jaw 
is  articulated  with  the  temporal  bone. 

Fig.  4.  The  posterior  and  right  Side  of  the 

Skull. 

A,  The  os  frontis.  B B,  The  ossa  parieta- 
lia.  C,  The  sagittal  suture.  D,  The  parie- 
tal hole,  through  which  a small  vein  runs  to 
the  superior  longitudinal  sinus.  E,  The  lamb- 
doid  suture.  F F,  Ossa  triquetra.  G,  The 
os  occipitis.  H,  The  squamous  part  of  the 
temporal  bone.  I,  The  mastoid  process.  K, 

S 


138 


Osteology. 


The  zygoma.  L,  The  os  ma be.  M,  The  tem- 
poral part  of  the  sphenoid  bone.  N,  The  su- 
perior maxillary  bone  and  teeth. 

Fig.  5.  The  external  Surface  of  the  OsFron- 

TIS. 

A,  The  convex  part.  B,  Part  of  the  tem- 
poral fossa.  C,  The  external  angular  process. 
D,  The  internal  angular  process.  E,  The  na- 
sal process.  F,  The  superciliary  arch.  G, 
The  superciliary  hole.  H,  The  orbitar  plate. 

Fig.  6.  The  Interior  Surface  of  the  OsFron- 

tis. 

A A,  The  serrated  edge  which  assists  to 
form  the  coronal  suture.  B,  The  external  an- 
gular process.  C,  The  internal  angular  pro- 
cess. D,  The  nasal  process.  E,  The  orbi- 
tar plate.  F,  The  cells  which  correspond  with 
those  of  the  ethmoid  bone.  G,  The  passage 
from  the  frontal  sinus.  H,  The  opening  which 
receives  the  cribriform  plate  of  the  ethmoid 
bone.  I,  The  cavity  which  lodges  the  fore 
part  of  the  brain.  K,  The  spine  to  which  the 
falx  is  fixed.  L,  The  groove  which  lodges 
the  superior  longitudinal  sinus. 

PLATE  XX. 

Fig.  1.  A Back-view  of  the  Skeleton. 

A A,  The  ossa  parietalia.  B,  The  sagit- 
tal suture.  C,  The  lambdoid  suture.  D,  The 


A N A.' I’  OMY 


Osteology. 


139 


occipital  bone.  E,  The  squamous  suture,  F, 
The  mastoid  process  of  the  temporal  bone. 
G,  The  os  malse.  H,  The  palate-plates  of  the 
superior  maxillary  bones.  I,  Tne  maxilla  in- 
ferior. K,  The  teeth  of  both  jaws.  L,  The 
seven  cervical  vertebras.  M,  Their  spinous 
processes.  N,  Their  transverse  and  oblique 
processes.  O,  The  last  of  the  twelve  dorsal 
vertebrae.  P,  The  fifth  or  last  lumbar  vertebra. 
Q,  The  transverse  processes.  R,  The  obli- 
que processes.  S,  The  spinous  processes.  T, 
The  upper  part  of  the  os  sacrum.  U,  The 
posterior  holes  which  transmit  small  blood- 
vessels and  nerves.  V,  The  under  part  of 
the  os  sacrum  which  is  covered  by  a mem- 
brane. W,  The  os  coccygis.  X,  The  os  ili- 
um. Y,  Its  spine  or  crest.  Z,  The  ischia- 
tic  niche,  a,  The  os  ischium,  b,  Its  tubero- 
sity. c,  Its  spine,  d,  The  os  pubis,  e,  The 
foramen  hydroideum.  f,  The  seventh  or  last 
true  rib.  g,  The  twelfth  or  last  false  rib.  h, 
The  clavicle,  i,  The  scapula,  k,  Its  spine. 
1,  Its  acromion,  m,  Its  cervix,  n,  Its  supe- 
rior costa,  o,  Its  posterior  costa-  p,  Its  infe- 
rior costa.  q,  The  os  humeri,  r,  The  radi- 
us. s,  The  ulna,  t,  Its  oleclarnon.  u,  All 
the  bones  of  the  carpus,  excepting  the  os  pi- 
siforme,  which  is  seen  in  plate  XIX.  fig.  1. 
v,  The  five  bones  of  the  metacarpus,  w,  The 
two  bones  of  the  thumb,  x,  The  three  bones 
of  each  of  the  fingers,  y,  The  two  sesamoid 
bones  at  the  root  of  the  left  thumb,  z,  The 
os  femoris.  1,  The  trochanter  major.  2,  The 


140  Osteology. 

trochanter  minor.  3,  The  linea  aspera.  4,  The 
internal  condyle.  5,  The  external  condyle.  6 6, 
The  semilunar  cartilages.  7,  The  tibia.  8,  The 
malleolus  internus.  9,  The  fibula.  10,  The 
malleolus  externus.  11,  The  tarsus.  12,  The 
metatarsus.  13,  The  toes- 

Fig-  2-  The  External  Surface  of  the  left  Os 
Parietale. 

A,  The  convex  smooth  surface-  B,  The  pari- 
etal hole.  C,  An  arch  made  by  the  beginning 
of  the  temporal  muscle- 

Hg.  3.  The  Internal  Surface  of  the  same  bone. 

A,  Its  superior  edge,  which,  joined  with 
the  other,  forms  the  sagittal  suture-  B,  The 
anterior  edge,  which  assists  in  the  formation 
of  the  coronal  suture.  C.  The  inferior  edge 
for  the  squamous  suture-  D,  The  posterior 
edge  for  the  lambdoid  suture.  E,  A depres- 
sion made  by  the  lateral  sinus-  F F,  The 
prints  of  the  arteries  of  the  dura  mater. 

Fig.  4.  The  External  Surface  of  the  Left  Os 
Temporum- 

A,  The  squamous  part-  B,  The  mastoid  pro- 
cess. C,  The  zygomatic  process.  D,  The 
styloid  process.  E,  The  petrosal  process.  F. 
The  meatus  auditorius  externus.  G,  The  gle- 
noid cavity  for  the  articulation  of  the  lower 
jaw.  H,  The  foramen  stylo-mastoideum  for 
the  portio  dura  of  the  seventh  pair  of  nerves 
I,  Passages  for  blood-vessels  into  the  bone.. 


Osteology,  141 

K,  The  foramen  mastoideum  through  which 
a vein  goes  to  the  lateral  sinus- 

Fig.  5.  The  Internal  Surface  of  the  Left  Os 
Temporum. 

A,  The  squamous  part;  the  upper  edge  of 
which  assists  in  forming  the  squamous  suture* 
B,  The  mastoid  process.  C,  The  styloid  pro- 
cess- D,  The  pars  petrosa.  E,  The  entry  of 
the  seventh  pair,  or  auditory  nefve.  F,  The 
fossa  which  lodges  a part  of  the  lateral  sinus- 
G,  The  foramen  mastoideum. 

Fig.  6.  The  External  Surface  of  the  Osse- 
ous Circle,  which  terminates  the  meatus 
auditorius  externus. 

A,  The  anterior  part.  B,  A small  part  of 
the  groove  in  which  the  membrana  tympani 
is  fixed. 

N-  B.  This  with  the  subsequent  bones  of 
the  ear,  are  here  delineated  as  large  as  the  life- 

Fig.  7-  The  Internal  Surface  of  the  Osseous 
Circle. 

A,  The  anterior  part-  B,  The  groove  in 
which  the  membrana  tympani  is  fixed- 

Fig-  8.  The  Situation  and  Connection  of  the 
Small  Bones  of  the  Ear. 

A,  The  malleus.  B,  The  incus-  C,  The  os 
orbiculare.  D>  The  stapes- 


142  Osteology. 

Fig.  9.  The  Malleus,  with  its  Head,  Handle, 
and  Small  processes. 

Fig.  10-  The  Incus,  with  its  Body,  Superior 
and  Inferior  Branches. 

Fig.  11*  The  Os  Orbiculare. 

Fig.  12-  The  Stapes,  with  its  Head,  Base, 
and  two  Crura. 

Fig-  13-  An  Internal  View  of  the  Labyrinth 
of  the  Ear. 

A,  The  hollow  part  of  the  cochlea,  which 
forms  a share  of  the  meatus  auditorius  inter- 
nus-  B,  The  vestibulum.  C C C,  The  semi- 
circular canals. 

Fig-  14-  An  External  View  of  the  Labyrinth. 

A,  The  semicircular  canals-  B,  The  fenes- 
tra ovalis  which  leads  into  the  vestibulum.  C, 
The  fenestra  rotunda  which  opens  into  the 
cochlea-  D,  The  different  turns  of  the  cochlea. 

Fig.  15*  The  Internal  Surface  of  the  Os  Sphe- 
noides. 

A A,  The  temporal  processes.  B B,  The 
pterygoid  processes-  C C,  The  spinous  pro- 
cesses. D D,  The  anterior  clinoid  processes. 
E,  The  posterior  clinoid  process-  F,  The  an- 
terior process  which  joins  the  ethmoid  bone. 
G,  The  sella  turcica  for  lodging  the  glandula 
pituitaria.  H,  The  foramen  opticum.  K,  The 
foramen  lacerum.  L,  The  foramen  rotun- 


Osteology.  143 

dum.  M,  The  foramen  ovale.  N,  The  fora- 
men spinale. 

Fig.  16.  The  External  Surface  of  the  Os 
Sphenoides. 

A A,  The  temporal  processes.  B B,  The 
pterygoid  processes.  C C,  The  spinous  pro- 
cesses. D,  The  processus  azygos.  E,  The 
small  triangular  processes  which  grow  from 
the  body  of  the  bone.  F F,  The  orifices  of 
the  sphenoidal  sinuses.  G,  The  foramen  la- 
cerum.  H,  The  foramen  rotundum.  I,  The 
foramen  ovale.  K,  The  foramen  pterygoide- 
um. 

Fig.  17.  The  External  View  of  the  Os  Eth- 

MOIDES- 

A,  The  nasal  lamella.  B B,  The  grooves 
between  the  nasal  lamella  and  ossa  spongiosa 
superiora.  C C,  The  ossa  spongiosa  superio- 
ra.  D D,  The  sphenoidal  cornua.  See  Fig. 
16.  E. 

Fig.  18.  The  Internal  View  of  the  Os  Eth- 

MOIDES* 

A,  The  crista  galli-  B,  The  cribriform 
plate,  with  the  different  passages  of  the  ol- 
factory nerves.  C C,  Some  of  the  ethmoidal 
cells.  D,  The  right  os  planum.  E E,  The 
sphenoidal  cornua. 

Fig.  19-  The  right  Sphenoidal  Cornu. 

Fi  g.  20.  The  left  Sphenoidal  Cornu. 


144  ' Osteology. 

Fig.  21.  The  External  Surface  of  the  Os  Oc* 
cipitis. 

A,  The  upper  part  of  the  bone.  B,  The 
superior  arched  ridge.  C,  The  inferior  arch- 
ed ridge.  Under  the  arches  are  prints  made 
by  the  muscles  of  the  neck.  D D,  The  two 
condyloid  processes  which  articulate  the  head 
with  the  spine.  E,  The  cuneiform  process. 
F,  The  foramen  magnum  through  which  the 
spinal  marrow  passes.  G G,  The  posterior 
condyloid  foramina  which  transmit  veins  into 
the  lateral  sinuses.  H H,  The  foramina  lin- 
gualia  for  the  passage  of  the  nine  pair  of 
nerves* 

Fig.  22.  The  Internal  Surface  of  the  Os  Oc- 

CIPITIS. 

A A,  The  two  sides  which  assist  to  form 
the  lambdoid  suture.  B,  The  point  of  the 
cuneiform  process,  where  it  joins  the  sphe- 
noid bone.  C C,  The  prints  made  by  the 
posterior  lobes  of  the  brain-  D D,  Prints 
made  by  the  lobes  of  the  cerebellum.  E,  The 
cruciform  ridge  for  the  attachment  of  the  pro- 
cesses of  the  dura  mater.  F,  The  course  of 
the  superior  longitudinal  sinuses.  G G,  The 
course  of  the  two  lateral  sinuses.  H,  The 
foramen  magnum.  II,  The  posterior  condy- 
loid foramina. 


* 


Osteology. 


145 


Plate  XXL 

Fig.  1*  A Side-view  of  the  Skeleton. 

A A,  The  ossa  parietalia.  B,  The  sagittal 
suture.  C,  The  os  occipitis.  D D,  The  lamb- 
doid  suture.  E,  The  squamous  part  of  the  tem- 
poral bone-  F,  The  mastoid  process.  G,  The 
meatus  auditorius  externus.  H,  Th,e  os  fron- 
tis.  I,  The  os  malse.  K,  The  os  maxillare 
superius.  L,  The  maxilla  inferior.  M,  The 
teeth  of  both  jaws.  N,  The  seventh,  or  last 
cervical  vertebra-  O,  The  spinous  processes. 
P,  Their  transverse  and  oblique  processes.  Q, 
The  twelfth  or  last  dorsal  vertebra-  R,  The 
fifth,  or  last  lumbar  vertebra.  S.  The  spinous 
processes.  T,  Openings  between  the  verte- 
brae for  the  passage  of  the  spinal  nerves.  U, 
The  under  end  of  the  os  sacrum.  V,  The 
os  coccygis.  W,  The  os  ilium.  X,  The  an- 
terior spinous  processes.  Y,  The  posterior 
spinous  processes.  Z,  The  ischiatic  niche-  a, 
The  right  os  ilium.  b,  The  ossa  pubis,  c, 
The  tuberosity  of  the  left  os  ischium,  d,  The 
scapula-  e,  Its  spine,  f,  The  os  humeri,  g, 
The  radius,  h,  The  ulna,  i,  The  carpus,  k, 
The  metacarpal  bone  of  the  thumb.  1,  The 
metacarpal  bones  of  the  fingers,  m.  The  two 
bones  of  the  thumb,  n,  The  three  bones  of 
each  of  the  fingers,  o,  The  os  femoris.  p, 
Its  head-  q,  The  trochanter  major,  r.  The 
external  condyle-  s,  The  rotula.  t,  The  tibia. 

T 


146  Osteology. 

u,  1 he  fibula,  v,  The  malleolus  externus. 
w,  The  astragalus,  x,  The  os  calcis.  y,  The 
os  naviculare.  z,  The  three  ossa  cuneiformia. 
1,  The  os  cuboides.  2,  The  five  metatarsal 
bones.  3,  The  two  bones  of  the  great  toe.  4, 
The  three  bones  of  each  of  the  small  toes. 

Fig.  2-  A View  of  the  Internal  Surface  of  the 
Base  of  the  Skull. 

AAA,  The  two  tables  of  the  skull  with 
the  diploe.  B B,  The  orbitar  plates  of  the 
frontal  bone.  C,  l he  crista  galli,  with  cribri- 
form plate  of  the  ethmoidal  bone  on  each  side 
of  it,  through  which  the  first  pair  of  nerves 
pass.  D,  The  cuneiform  process  of  the  occipi- 
tal bone.  E,  The  cruciform  ridge.  F,  The 
foramen  magnum  for  the  passage  of  the  spi- 
nal marrow.  G,  The  zygoma,  made  by  the 
joining  of  the  zygomatic  processes  of  the  os 
temporum  and  os  malse.  H,  'I  he  pars  squa- 
mosa of  the  os  temporum.  I,  The  pars  mam- 
millaris.  K,  The  pars  petrosa.  L,  The  tem- 
poral process  of  the  sphenoid  bone.  M M, 
The  anterior  clinoid  processes.  N,  The  pos- 
terior clinoid  process.  O,  The  sella  turcica. 
P,  The  foramen  opticum,  for  the  passage  of 
the  optic  nerve  and  ocular  artery  of  the  left 
side.  Q,  The  foramen  lacerum,  for  the  third, 
fourth,  sixth,  and  first  of  the  fifth  pair  of  nerves 
and  ocular  vein.  R,  The  foramen  rotundum, 
for  the  second  of  the  fifth  pair.  S,  The  fora- 
men ovale,  for  the  third  of  the  fifth  pair.  T, 
The  foramen  spinale,  for  the  principal  artery 
of  the  dura  mater,  U,  The  entry  of  the  au- 


Osteology.  147 

ditory  nerve-  V,  The  passage  for  the  lateral 
sinus.  W,  The  passage  of  the  eighth  pair  of 
nerves.  X,  The  passage  of  the  ninth  pair- 

Fig.  3*  A View  of  the  External  Surface  of  the 
Base  of  the  Skull. 

A,  The  two  dentes  incisores  of  the  right 
side.  B,  The  dens  caninus-  C,  The  two  small 
molares.  D,  The  three  large  molares.  E,  The 
foramen  incisivum,  which  gives  passage  to 
small  blood-vessels  and  nerves.  F,  The  palate- 
plates  of  the  ossa  maxillaria  and  palati,  joined 
by  the  longitudinal  and  transverse  palate  su- 
tures. G,  The  foramen  palatinum  posterius, 
for  the  palatine  vessels  and  nerves-  H,  The 
os  maxillare  superius  of  the  right  side.  1,  The 
os  malas.  K,  The  zygomatic  process  of  the 
temporal  bone.  L,  1 he  posterior  extremity  of 
the  ossa  spongiosa.  M,  The  posterior  extre- 
mity of  the  vomer,  which  forms  the  back-part 
of  the  septum  nasi.  N,  The  pterygoid  process 
of  the  right  side  of  the  sphenoid  bone.  O O,  The 
foramina  ovalia.  PP,  The  foramina  spinalia. 
Q,  Q,,  The  passages  of  the  internal  carotid  ar- 
teries. R,  A hole  between  the  point  of  each  pars 
petrosa  and  cuneiform  process  of  the  occipital 
bone,  which  is  filled  up  with  a ligamentous  sub- 
stance in  the  recent  subject.  S,  The  passage 
of  the  left  lateral  sinus.  T,  The  posterior 
condyloid  foramen  of  the  left  side-  U,  The 
foramen  mastoideum.  V,  The  foramen  mag- 
num. W,  The  inferior  orbitar  fissure.  X,  The 
glenoid  cavity,  for  the  articulation  of  the  low- 
er jaw.  Y,  The  squamous  part  of  the  temporal 


148 


Osteology. 


bone.  Z,  The  mastoid  process,  at  the  inner 
side  of  which  is  a fossa  for  the  posterior  belly 
of  the  digastric  muscle,  a,  I he  styloid  pro- 
cess. b,  1 he  meatus  auditorius  externus.  c, 
The  left  condyle  of  the  occipital  bone,  d,  The 
perpendicular  occipital  spine,  e e,  The  infe-i 
rior  horizontal  ridge  of  the  occipital  bone,  f f, 
The  superior  horizontal  ridge,  which  is  oppo- 
site to  the  crucial  ridge  where  the  longitudinal 
sinus  divides  to  form  the  lateral  sinuses,  g g g, 
The  lambdoid  suture,  h,  The  left  squamous  su- 
ture. i,  The  parietal  bone- 

Fig.  4.  The  anterior  surface  of  the  Ossa 

Nasi. 

A,  The  upper  part,  which  joins  the  os  fron- 
tis.  B,  The  under  end,  which  joins  the  car- 
tilage of  the  nose.  C,  The  inner  edge,  where 
they  join  each  other. 

Fig.  5.  The  posterior  surface  of  the  Ossa 

Nasi. 

A A,  Their  cavity,  which  forms  part  of  the 
arch  of  the  nose.  B B,  Their  ridge  or  spine, 
which  projects  a little  to  be  fixed  to  the  fore- 
part of  the  septum  narium. 

Fig.  6.  The  external  surface  of  the  Os  Max- 
illare  Superius  of  the  left  side. 

A,  The  nasal  process.  B,  The  orbitar 
plate.  C,  The  unequal  surface  which  joins 
the  os  make.  D,  The  external  orbitar  hole. 
E,  The  opening  into  the  nostril.  F,  The  pa- 


Osteology. 


149 


late-plate.  G,  The  maxillary  tuberosity.  H, 
Part  of  the  os  palati.  I,  The  two  dentes  inci- 
sores.  K,  The  dens  caninus.  L,  The  two 
small  dentes  molares.  M,  The  three  large 
dentes  molares. 

Fig.  7.  The  internal  surface  of  the  Os  Max- 
ill are  Superius  and  Os  Palati. 

A,  The  nasal  process.  B B,  Eminences  for 
the  connection  of  the  os  spongiosum  inferius. 

D,  The  under  end  of  the  lachrymal  groove. 

E,  Tne  antrum  maxillare.  E,  The  nasal  spine, 
between  which  and  B is  the  cavity  of  the  nos- 
tril. G,  The  palate-plate.  H,  The  orbitar 
part  of  the  os  palati.  I,  The  nasal  plate.  K, 
The  suture  which  unites  the  maxillary  and  pa- 
late bones.  L,  The  pterygoid  process  of  the 
palate  bones. 

Fig.  8.  The  external  surface  of  the  right  Os 
Unguis. 

A,  The  orbitar  part.  B,  The  lachrymal  part, 
C,  The  ridge  between  them. 

Fig.  9.  The  internal  surface  of  the  right  Os 
Unguis. 

This  side  of  the  bone  has  a furrow  opposite 
to  the  external  ridge  ; all  behind  that  is  irre- 
gular, where  it  covers  part  of  the  ethmoidal 
cells. 


150  Osteology. 


Fig.  10.  The  external  surface  of  the  left  Os 

Mal£. 

A,  The  superior  orbitar  process.  B,  The 
inferior  orbitar  process.  C,  The  malar  pro- 
cess. D,  The  zygomatic  process.  E,  The 
orbitar  plate.  F,  A passage  for  small  vessels 
into  or  out  of  the  orbit. 

Fig.  11.  The  internal  surface  of  the  left  Os 

Malje. 


A,  The  superior  orbitar  process.  B,  The 
inferior  orbitar  process.  C,  The  malar  pro- 
cess. D,  The  zygomatic  process.  E,  The 
internal  orbitar  plate  or  process. 


^ig.  12.  The  external  surface  of  the  right  Os 
Spongiosum  Infeiuus. 

A,  The  anterior  part.  B,  The  hook-like 
process  for  covering  part  of  the  antrum  maxil- 
lare.  C,  \ small  process  which  covers  part 
of  the  under  end  of  the  lachrymal  groove. 
D,  The  inferior  edge  turned  a little  outwards. 

Fig.  13.  The  internal  surface  of  the  Os  Spon- 
giosum Inferius. 

A,  The  anterior  extremity.  B,  The  upper 
edge  which  joins  the  superior  maxillary  and 
palate  bones- 

Fig.  14.  The  posterior  and  external  surface 
of  the  right  Os  Palati. 

A,  The  orbitar  process.  B,  The  nasal  la- 
mella. C,  The  pterygoid  process.  D,  The 
palate  process. 


Osteology . 


151 


Fig.  15.  The  anterior  and  external  surface 
of  the  right  Os  Palati. 

A,  The  orbitar  process.  B,  An  opening 
through  which  the  lateral  nasal  vessels  and 
nerves  pass.  C,  The  nasal  lamella.  D,  The 
pterygoid  process.  E,  The  posterior  edge  of 
the  palate  process  for  the  connection  of  the 
velum  palati.  F,  The  inner  edge  by  which 
the  two  ossa  palati  are  connected. 

Fig.  16-  The  right  side  of  the  Vomer. 

A,  The  upper  edge  which  joins  the  nasal 
lamella  of  the  ethmoid  bone  and  the  middle 
cartilage  of  the  nose.  B,  The  inferior  edge, 
which  is  connected  to  the  superior  maxillary 
and  palate  bones.  C,  The  superior  and  pos- 
terior part  which  receives  the  processus  azy- 
gos of  the  sphenoid  bone. 

Fig.  17-  The  Maxilla  Inferior. 

A,  The  chin*  B,  The  base  and  left  side. 
C,  The  angle.  D,  The  coronoid  process.  E, 
The  condyloid  process.  F,  The  beginning  of 
the  inferior  maxillary  canal  of  the  right  side, 
for  the  entry  of  the  nerve  and  blood-vessels. 
G,  The  termination  of  the  left  canal-  H,  The 
two  dentes  incisores.  I,  The  dens  caninus.  K, 
The  two  small  molares.  L,  The  three  large 
molares. 

Fig.  18.  The  different  classes  of  the  Teeth. 

1,  2,  A fore  and  back  view  of  the  two  ante- 
rior dentes  incisores  of  the  lower  jaw.  3,  4, 


152  Osteology. 

Similar  teeth  of  the  upper  jaw.  5,  6,  A fore 
and  back  view  of  the  dentes  canini.  7,  8, 
The  anterior  dentes  molares.  9,  10,  11,  The 
posterior  dentes  molares.  12,  13,  14,  15,  16, 
Unusual  appearances  in  the  shape  and  size  of 
the  teeth. 

Fig.  19.  The  external  surface  of  the  Os  Hy 

OIDES. 

A,  The  body.  B B,  The  cornua.  C C, 
The  appendices. 


Plate  XXII. 

Fig.  1.  A Posterior  View  of  the  Sternum 
and  Clavicles,  with  the  ligament  connect- 
ing the  clavicles  to  each  other. 

a,  The  posterior  surface  of  the  sternum, 
b b,  The  broken  ends  of  the  clavicles-  c c c c, 
The  tubercles  near  the  extremity  of  each  cla- 
vicle. d,  The  ligament  connecting  the  cla- 
vicles. 

Fig.  2.  A Fore-view  of  the  Left  Scapula, 
and  of  a half  of  the  Clavicle,  with  their 
Ligaments. 

a,  The  spine  of  the  scapula,  b,  the  acro- 
mion. c,  The  inferior  angle-  d,  Inferior  cos- 
ta. e,  Cervix,  f,  Glenoid  cavity,  covered 
with  cartilage  for  the  arm-bone,  g g,  The 
capsular  ligament  of  the  joint-  h,  Coracoid 


' 


Osteology.  153 

process,  i,  The  broken  end  of  the  clavicle, 
k,  Its  extremity  joined  to  the  acromion.  1,  A 
ligament  coming  out  single  from  the  acromion 
to  the  coracoid  process,  m,  A ligament  com- 
ing out  single  from  the  acromion,  and  dividing 
into  two,  which  are  fixed  to  the  coracoid  pro- 
cess- 

Fig.  3.  The  Joint  of  the  Elbow  of  the  Left 
Arm,  with  the  Ligaments. 

a,  The  os  humeri,  b,  Its  internal  condyle, 
c c,  The  two  prominent  parts  of  its  trochlea 
appearing  through  the  capsular  ligament,  d, 
The  ulna,  e,  The  radius,  f,  The  part  of  the 
ligament  including  the  head  of  the  radius. 

Fig.  4.  The  Bones  of  the  Right-Hand,  with 
the  Palm  in  view. 

a,  The  radius,  b,  The  ulna,  c,  The  sca- 
phoid bone  of  the  carpus,  d,  The  os  lunare. 
e,  The  os  cuneiforme.  f,  The  os  pisiforme. 
g,  Trapezium,  h,  Trapezoides.  i,  Capita- 
turn.  k,  Unciforme.  1,  The  four  metacar- 
pal bones  of  the  fingers,  m,  The  first  pha- 
lanx. n,  The  second  phalanx,  o,  The  third 
phalanx,  p,  The  metacarpal  bone  of  the 
thumb,  q,  The  first  joint,  r,  The  second 
joint. 

Fig.  5.  The  Posterior  View  of  the  Bones  of 
the  Left  Hand- 

The  explication  of  Fig.  4.  serves  for  this 
figure  ; the  same  letters  pointing  out  the  same 
bones,  though  in  a different  view. 

U 


154 


Osteology. 


Fig.  6.  The  Upper  Extremity  of  tlie  Tibia, 
with  the  Semilunar  Cartilages  of  the  Joint 
of  the  Knee,  and  some  Ligaments. 

a,  The  strong  ligament  which  connects 
the  rotula  to  the  tubercle  of  the  tibia,  b b, 
The  parts  of  the  extremity  of  the  tibia,  co- 
vered with  cartilage,  which  appear  within  the 
semilunar  cartilages*  c c,  The  semilunar  car- 
tilages- d,  The  two  parts  of  what  is  called 
the  cross  ligament. 

Fig-  7-  The  Posterior  View  of  the  Joint  of 
the  Right  Knee. 

a,  The  os  femoris  cut-  b,  Its  internal  con- 
dyle. c,  Its  external  condyle,  d,  The  back 
part  of  the  tibia,  e,  The  superior  extremity 
of  the  fibula,  f,  The  edge  of  the  internal  se- 
milunar cartilage,  g,  An  oblique  ligament. 

h,  A larger  perpendicular  ligament,  i,  A li- 
gament connecting  the  femur  and  fibula. 

Fig.  8-  The  Anterior  View  of  the  Joint  of 
the  Right  Knee. 

b,  The  internal  condyle*  c,  Its  external 
condyle,  d,  The  part  of  the  os  femoris,  on 
which  the  patella  moves,  e,  A perpendicu- 
lar ligament,  f f,  The  two  parts  of  the  cru- 
cial ligaments,  g g,  The  edges  of  the  two 
moveable  semilunar  cartilages,  h,  The  tibia. 

i,  The  strong  ligament  of  the  patella,  k,  The 
back  part  of  it  where  the  fat  has  been  dis- 
sected away.  1,  The  external  depression,  m, 
The  internal  one.  n,  The  cut  tibia. 


Osteology. 


155 


Fig.  9.  A View  of  the  inferior  part  of  the 
Bones  of  the  Right  Foot. 

a,  The  great  knob  of  the  os  calcis.  b,  A 
prominence  on  its  outside,  c,  The  hollow 
for  the  tendons,  nerves,  and  blood-vessels,  d, 
The  anterior  extremity  of  the  os  calcis.  e, 
Part  of  the  astragalus,  f,  Its  head  covered 
with  cartilage,  g,  The  internal  prominence 
of  the  os  naviculare.  h,  The  os  cuboides. 
i,  The  os  cuneiforme  internum;  k, — Medium; 
1, — Externum,  m,  The  metatarsal  bones  of 
the  four  lesser  toes,  n,  The  first — o,  The 
second — p,  The  third  phalanx  of  the  four  les- 
ser toes,  q,  The  metatarsal  bones  of  the  great 
toe.  r,  Its  first — s,  Its  second  joint. 

Fig.  10.  The  Inferior  Surface  of  the  two  large 

Sesamoid  Bones,  at  the  first  Joint  of  the 

Great  Toe. 

Fig.  11*  The  Superior  View  of  the  Bones  of 
the  Right  Foot. 

a,  b,  as  in  Fig.  9.  c,  The  superior  head  of 
the  astragalus,  d,  &c.  as  in  Fig.  9. 

Fig.  12.  The  View  of  the  Sole  of  the  Foot, 
with  its  Ligaments. 

a,  The  great  knob  of  the  os  calcis.  b,  The 
hollow  for  the  tendons,  nerves,  and  blood- 
vessels. c,  The  sheaths  of  the  fiexores  pol- 
licis  and  digitorum  longi  opened,  d,  The 
strong  cartilaginous  ligament  supporting  the 
head  of  the  astragalus,  e,  h,  Two  ligaments 
which  unite  into  one,  and  are  fixed  to  the 


156 


Osteology. 


metatarsal  bone  of  the  great  toe.  f,  A liga- 
ment from  the  knob  of  the  os  calcis  to  the 
metatarsal  bone  of  the  little  toe.  g,  A strong 
triangular  ligament,  which  supports  the  bones 
of  the  tarsus,  i,  The  ligaments  of  the  joints 
of  the  five  metatarsal  bones. 

Fig.  13.  a,  The  head  of  the  thigh  bone  of 
a child,  b,  The  ligamentum  rotundum  con- 
necting it  to  the  acetabulum,  c,  The  capsu- 
lar ligament  of  the  joint  with  its  arteries  in- 
jected. d,  The  numerous  vessels  of  the  mu- 
cilaginous gland  injected. 

Fig.  14.  The  Back-view  of  the  Cartilages  of 
the  Larynx,  with  the  Os  Hyoides. 

a,  The  posterior  part  of  the  base  of  the  os 
hyoides.  b b,  Its  cornua,  c,  The  appendix 
of  the  right  side,  d,  A ligament  sent  out 
from  the  appendix  of  the  left  side,  to  the  sty- 
loid process  of  the  temporal  bone,  e,  The 
union  of  the  base  with  the  left  cornu,  f f, 
The  posterior  sides  of  (g)  the  thyroid  carti- 
lage. h h,  Its  superior  cornua,  i i,  Its  in- 
ferior cornua,  k,  The  cricoid  cartilage.  1 1, 
The  arytenoid  cartilages,  m,  The  entry  into 
the  lungs,  named  glottis,  n,  The  epiglottis, 
o o,  The  superior  cartilages  of  the  trachea, 
p,  Its  ligamentous  back  part. 

Fig.  15.  The  Superior  Concave  surface  of  the 
Sesamoid  Bones  at  the  first  joint  of  the 
Great  Toe,  with  their  Ligaments, 
a,  Three  sesamoid  bones,  b,  The  liga- 
mentous substance  in  which  they  are  formed. 


Of  the  Integuments , &c. 


157 


Part  II.  OF  THE  SOFT  PARTS  IN  GE- 
NERAL ; 


Of  the  Common  Integuments , with  their  appen- 
dages ; and  of  the  Muscles. 

ANATOMICAL  writers  usually  proceed 
to  a description A>f  the  muscles  after 
having  finished  the  osteology ; but  we  shall 
deviate  a little  from  the  common  method,  with 
a view  to  describe  every  thing  clearly  and  dis- 
tinctly, and  to  avoid  a tautology  which  would 
otherwise  be  unavoidable.  All  the  parts  of 
the  body  are  so  intimately  connected  with  each 
other,  that  it  seems  impossible  to  convey  a just 
idea  of  any  one  of  them,  without  being  in  some 
measure  obliged  to  say  something  of  others ; 
and  on  this  account  we  wish  to  mention  in  this 
place  the  names  and  situation  of  the  principal 
viscera  of  the  body,  that  when  mention  is 
hereafter  made  of  any  one  of  them  in  the 
course  of  the  work,  the  reader  may  at  least 
know  where  they  are  placed. 

After  this  little  digression,  the  common  in- 
teguments, and  after  them  the  muscles  will  be 
described ; we  then  propose  to  enter  into  an 
examination  of  the  several  viscera  and  their 
different  functions.  In  describing  the  brain. 


158  Of  the  Integuments , &c. 

occasion  will  be  taken  to  speak  of  the  nerves 
and  animal  spirits.  The  circulation  of  the 
blood  will  follow  the  anatomy  of  the  heart,  and 
the  secretions  and  other  matters  will  be  intro- 
duced in  their  proper  places. 

The  body  is  divided  into  three  great  cavities. 
Of  these  the  uppermost  is  formed  by  the  bones 
of  the  cranium,  and  incloses  the  brain  and  cere- 
bellum. 

The  second  is  composed  of  the  vertebrse  of 
the  back,  the  sternum,  and  true  ribs,  with  the 
additional  assistance  of  muscles,  membranes, 
and  common  integuments,  and  is  called  the 
thorax — It  contains  the  heart  and  lungs. 

The  third,  and  inferior  cavity,  is  the  abdo- 
men. It  is  separated  from  the  thorax  by 
means  of  the  diaphragm,  and  is  formed  by 
the  lumbar  vertebrae,  the  os  sacrum,  the  os- 
sa innominata,  and  the  false  ribs,  to  which  we 
may  add  the  peritonaeum,  and  a variety  of 
muscles.  This  cavity  incloses  the  stomach, 
intestines,  omentum  or  cawl,  liver,  pancreas, 
spleen,  kidneys,  urinary  bladder,  and  parts  of 
generation. 

Under  the  division  of  common  integuments 
are  usually  included  the  epidermis,  or  scarf- 
skin,  the  reticulum  mucosum  of  Malpighi, 
the  cutis  or  true  skin,  and  the  membrana  adi- 
posa — The  hair  and  nails,  as  well  as  the  se- 
baceous glands,  may  be  considered  as  appen- 
dages to  the  skin. 


Of  the  Integuments , &c. 


159 


Sect.  I.  Of  the  Skin. 

1.  Of  the  Scarf -skin. 

The  epidermis,  cuticula,  or  scarf-skin,  is 
a fine,  transparent,  and  insensible  pellicle,  des- 
titute of  nerves  and  blood-vessels,  which  in- 
vests the  body,  and  every  where  covers  the 
true  skin.  This  scarf-skin,  which  seems  to 
be  very  simple,  appears,  when  examined  with 
a microscope,  to  be  composed  of  several  la- 
minse  or  scales  which  are  increased  by  pres- 
sure, as  we  may  observe  in  the  hands  and 
feet,  where  it  is  frequently  much  thickened, 
and  becomes  perfectly  callous.  It  seems  to 
adhere  to  the  cutis  by  a number  of  very  mi- 
nute filaments,  but  may  easily  be  separated 
from  it  by  heat,  or  by  maceration  in  water- 
Some  anatomical  writers  have  supposed  that  it 
is  formed  by  a moisture  exhaled  from  the  whole 
surface  of  the  body,  which  gradually  hardens 
when  it  comes  into  contact  with  the  air.  They 
were  perhaps  induced  to  adopt  this  opinion, 
by  observing  the  speedy  regeneration  of  this 
part  of  the  body  when  it  has  been  by  any  means 
destroyed,  it  appearing  to  be  renewed  on  all 
parts  of  the  surface  at  the  same  time ; where- 
as other  parts  which  have  been  injured,  are 
found  to  direct  their  growth  from  their  circum- 
ference only  towards  their  centre.  But  a demon- 
strative proof  that  the  epidermis  is  not  a fluid 


160 


Of  the  Integuments , &d. 


hardened  by  means  of  the  external  air,  is  that 
the  foetus  in  utero  is  found  to  have  this  cover- 
ing. Lieuwenhocck  supposed  its  formation  to 
be  owing  to  the  expansion  of  the  extremities 
of  the  excretory  vessels  which  are  found  eve- 
ry where  upon  the  surface  of  the  true  skin. 
Ruysch  attributed  its  origin  to  the  nervous 
papillae  of  the  skin;  and  Heister  thinks  it  pro- 
bable, that  it  may  be  owing  both  to  the  pa- 
pillae and  the  excretory  vessels.  The  cele- 
brated Morgagni,  on  the  other  hand,  contends,* 
that  it  is  nothing  more  than  the  surface  of  the 
cutis,  hardened  and  rendered  insensible  by  the 
liquor  amnii  in  utero,  and  by  the  pressure  of 
the  air.  This  is  a subject,  however,  on  which 
we  can  advance  nothing  with  certainty. 

The  cuticle  is  pierced  with  an  infinite  num- 
ber of  pores  or  little  holes,  which  afford  a 
passage  to  the  hairs,  sweat,  and  insensible  per- 
spiration, and  likewise  to  warm  water,  mer- 
cury, and  whatever  else  is  capable  of  being 
taken  in  by  the  absorbents  of  the  skin.  The 
lines  which  we  observe  on  the  epidermis  be- 
long to  the  true  skin.  The  cuticle  adjusts  it- 
self to  them,  but  does  not  form  them- 

2.  Of  the  Rete  Mucosum. 

Between  the  epidermis  and  cutis  we  meet 
with  an  appearance  to  which  Malpighi,  who 
first  described  it,  gave  the  name  of  rete  muco- 
sum, supposing  it  to  be  of  a membranous 
structure,  and  pierced  with  an  infinite  number 
of  pores;  but  the  fact  is,  that  it  seems  to  be 

* Adversar.  Anat.  n.  Animadver.  2. 


161 


Of  the  Integuments , &?c. 

nothing  more  than  a mucous  substance  which 
may  be  dissolved  by  macerating  it  in  water, 
while  the  cuticle  and  cutis  preserve  their  tex- 
ture. 

The  colour  of  the  body  is  found  to  depend 
on  the  colour  of  this  rete  mucosum  ; for  in  ne- 
groes it  is  observed  to  be  perfectly  black,  whilst 
the  true  skin  is  of  the  ordinary  colour. 

The  blisters  which  raise  the  skin  when  burnt 
or  scalded,  have  been  supposed  by  some  to  be 
owing  to  a rarefaction  of  this  mucus  ; but  they 
are  more  probably  occasioned  by  an  increased 
action  of  the  vessels  of  the  part,  together  with 
an  afflux  and  effusion  of  the  thinner  parts  of 
the  blood* 

.3.  Of  the  Cutis,  or  True  Ski?i. 

The  cutis  is  composed  of  fibres  closely 
compacted  together,  as  we  may  observe  in  lea- 
ther, which  is  the  prepared  skin  of  animals. 
These  fibres  form  a thick  net-work,  which 
every  where  admits  the  filaments  of  nerves, 
and  an  infinite  number  of  blood-vessels  and 
lymphatics. 

The  cutis,  when  the  epidermis  is  taken  off, 
is  found  to  have,  throughout  its  whole  sur- 
face, innumerable  papillae,  which  appear  like 
very  minute  granulations,  and  seem  to  be  cal- 
culated to  receive  the  impressions  of  the  touch, 
being  the  most  easily  observed  where  the  sense 
of  feeling  is  the  most  delicate,  as  in  the  palms 
of  the  hands  and  on  the  fingers. 

X 


162 


Of  the  Integuments , &c. 

These  papillae  are  supposed  by  many  ana- 
tomical writers  to  be  continuations  of  the  pul- 
py substance  of  nerves,  whose  coats  have  ter- 
minated in  the  cellular  texture  of  the  skin. 
The  great  sensibility  of  these  papillae  evi- 
dently proves  them  to  be  exceedingly  nervous  ; 
but  surely  the  nervous  fibre  llae  of  the  skin  are 
pf  themselves  scarcely  equal  to  the  formation 
of  these  papillae,  and  it  seems  to  be  more  pro- 
bable that  they  are  formed  like  the  rest  of  the 
cutis. 

These  papillae  being  described,  the  uses  of 
the  epidermis  and  the  reticulum  mucosum  will 
be  more  easily  understood ; the  latter  serving 
to  keep  them  constantly  moist,  while  the  for- 
mer protects  them  from  the  external  air,  and 
modifies  their  too  great  sensibility. 

4.  Of  the  Glands  of  the  Skin. 

In  different  parts  of  the  body  we  meet, 
within  the  substance  of  the  skin,  with  certain 
glands  or  follicles,  which  discharge  a fat  and 
oily  humour  that  serves  to  lubricate  and  soft- 
en the  skin.  When  the  fluid  they  secrete 
has  acquired  a certain  degree  of  thickness,  it 
approaches  to  the  colour  and  consistence  of 
suet ; and  from  this  appearance  they  have  de- 
rived their  name  of  sebaceous  glands.  They 
are  found  in  the  greatest  number  in  the  nose, 
ear,  nipple,  axilla,  groin,  scrotum,  vagina,, 
and  prepuce. 

Besides  these  sebaceous  glands,  we  read, 
in  anatomical  books,  of  others  that  are  de- 


Of  the  Integuments , &c.  163 

scribed  as  small  spherical  bodies  placed  in  all 
parts  of  the  skin,  in  much  greater  abundance 
than  those  just  now  mentioned,  and  named  mi- 
liary, from  their  supposed  resemblance  to  mil- 
let-seed. Steno,  who  first  described  these 
glands,  and  Malpighi,  Ruysch,  Verheyen, 
Windslow,  and  others,  who  have  adopted  his 
opinions  on  this  subject,  speak  of  them  as  hav- 
ing excretory  ducts,  that  open  on  the  surface 
of  the  cuticle,  and  distil  the  sweat  and  mat- 
ter of  insensible  perspiration  ; and  yet,  not- 
withstanding the  positive  manner  in  which  these 
pretended  glands  have  been  spoken  of,  we  are 
now  sufficiently  convinced  that  their  existence 
is  altogether  imaginary. 

5.  Of  the  Insensible  Perspiration  and  Sweat. 

The  matter  of  insensible  perspiration,  or  in 
other  words,  the  subtile  vapour  that  is  continu  - 
ally exhaling  from  the  surface  of  the  body,  is 
not  secreted  by  any  particular  glands,  but 
seems  to  be  derived  wholly  from  the  extremities 
of  the  minute  arteries  that  are  everywhere  dis- 
persed through  the  skin.  These  exhaling  ves- 
sels are  easily  demonstrated  in  the  dead  sub- 
ject, by  throwing  water  into  the  arteries  ; for 
then  small  drops  exude  from  all  parts  of  the 
skin,  and  raise  up  the  cuticle,  the  pores  of  which 
are  closed  by  death  ; and  in  the  living  subject, 
a looking-glass  placed  against  the  skin,  is  soon 
obscured  by  the  vapour.  Bidioo  fancied  he 
had  discovered  ducts  leading  from  the  cutis  to 


164  Of  the  Integuments , &c. 

the  cuticle,  and  transmitting  this  fluid  ; but  in 
this  he  was  mistaken. 

When  the  perspiration  is  by  any  means  in- 
creased, and  several  drops  that  were  insensi- 
ble when  separate,  are  united  together  and  con- 
densed by  the  external  air,  they  form  upon 
the  skin  small,  but  visible,  drops  called  sweat* ** 
This  particularly  happens  after  much  exercise, 
or  whatever  occasions  an  increased  determin- 
ation of  fluids  to  the  surface  of  the  body  ; a 
greater  quantity  of  perspirable  matter  being 
in  such  cases  carried  through  the  passages  that 
are  destined  to  convey  it  off. 

It  has  been  disputed,  indeed,  whether  the 
insensible  perspiration  and  sweat  are  to  be 
considered  as  one  and  the  same  excretion,  dif- 
fering only  in  degree ; or  whether  they  are 
two  distinct  excretions  derived  from  different 
sources.  In  support  of  the  latter  opinion,  it 
has  been  alleged,  that  the  insensible  perspi- 
ration is  agreeable  to  nature,  and  essential  to 
health,  whereas  sweat  may  be  considered  as  a 
species  of  disease.  But  this  argument  proves 
nothing  ; and  it  seems  probable,  that  both  the 
insensible  vapour  and  the  sweat  are  exhaled 
in  a similar  manner,  though  they  differ  in 
quantity,  and  probably  in  their  qualities  ; the 
former  being  more  limpid,  and  seemingly  less 
impregnated  with  salts  than  the  latter  : at  any 
rate  we  may  consider  the  skin  as  an  emuncto- 
ry  through  which  the  redundant  water,  and 

* Lieuwenhoeck  asserts  that  one  drop  of  sweat  is  formed  by 

the  conflux  of  fifteen  drops  of  perspirable  vapour. 


.i Of  the  Integuments , &c. 


165 


sometimes  the  other  more  saline  parts  of  the 
blood,  are  carried  off.  But  the  insensible  per- 
spiration is  not  confined  to  the  skin  only — a 
great  part  of  what  we  are  constantly  throwing 
off  in  this  way  is  from  the  lungs.  The  quantity 
of  fluid  exhaled  from  the  human  body  by  this 
insensible  perspiration  is  very  considerable. 
Sanctorius*  an  Italian  physician,  who  indefati- 
gably  passed  a great  many  years  in  a series  of  sta- 
tical experiments,  demonstrated  long  ago  what 
has  been  confirmed  by  later  observations,  that 
the  quantity  of  vapour  exhaled  from  the  skin 
and  from  the  surface  of  the  lungs,  amounts 
nearly  to  5-8ths  of  the  aliment  we  take  in.  So 
that  if  in  the  warm  climate  of  Italy  a person  eats 
and  drinks  the  quantity  of  eight  pounds  in  the 
course  of  a day,  five  pounds  of  it  will  pass  off 
by  insensible  perspiration,  while  three  pounds 
only  will  be  evacuated  by  stool,  urine,  saliva, 
&c.  But  in  countries  where  the  degree  of 
cold  is  greater  than  in  Italy,  the  quantity  of 
perspired  matter  is  less ; in  some  of  the  more 
northern  climates,  it  being  found  not  to  equal 
the  discharge  by  urine.  It  is  likewise  observ- 

* The  inseTi'sible  perspiration  is  sometimes  distinguished  by 
the  narr.e  of  this  physician,  who  was  born  in  the  territories  of 
Venice,  and  was  afterwards  a professor  in  the  university  of  Pa- 
dua. After  estimating  the  aliment  he  took  in,  and  the  sensible 
secretions  and  discharges,  he  was  enabled  to  ascertain  with  great 
accuracy  the  weight  or  quantity  of  insendble  perspiration  by 
means  of  a statical  chair  which  he  contrived  for  this  purpose;  and 
from  his  experiments,  which  were  conducted  with  great  industry 
and  patience,  he  was  led  to  determine  what  kinds  of  solid  or  li- 
quid aliment  increased  or  diminished  it.  From  these  experi- 
ments he  formed  a system,  which  he  published  at  Venice  in  1614, 
in  the  form  of  aphorisms,  under  the  title  of  61  Ars  de  Medicina 
Statica.” 


166 


Of  the  Integuments , &c. 


ed  to  vary  according  to  the  season  of  the 
year,  and  according  to  the  constitution,  age, 
4Slx,  diseases,  diet,  exercise,  passions,  fkc.  of 
different  people. 

From  what  has  been  said  on  this  subject,  it 
will  be  easily  conceived,  that  this  evacuation 
cannot  be  either  much  increased  or  diminish- 
ed in  quantity  without  affecting  the  health. 

The  perspirable  matter  and  the  sweat  are  in 
some  measure  analogous  to  the  urine,  as  ap- 
pears from  their  taste  and  saline  nature.*  And 
it  is  worthy  of  observation,  that  when  either 
of  these  secretions  is  increased  in  quantity, 
the  other  is  diminished  ; so  that  they  who  per- 
spire the  least,  usually  pass  the  greatest  quan- 
tity of  urine,  and  vice  versa. 

6.  Of  the  Nails, 

The  nails  are  of  a compact  texture,  hard 
and  transparent  like  horn.  Their  origin  is 
still  a subject  of  dispute.  Malpighi  supposed 
them  to  be  formed  by  a continuation  of  the 
papillae  of  the  skin : Ludwig,  on  the  other  hand, 
maintained,  that  they  were  composed  of  the 
extremities  of  blood-vessels  and  nerves ; both 
these  opinions  are  now  deservedly  rejected. 

They  seem  to  possess  many  properties  in 
common  with  the  cuticle ; like  it  they  are  nei- 
ther vascular  nor  sensible,  and  when  the  cuti- 

* Minute  chrystals  have  been  observed  to  shoot  upon  the 
clothes  of  men  who  work  in  glass-houses.  Haller  E/em.  Phys. 


Of  the  Integuments , &c. 


167 


cle  is  separated  from  the  true  skin  by  macera- 
tion or  other  means,  the  nails  come  away  with 
it. 

They  appear  to  be  composed  of  different 
layers,  of  unequal  size,  applied  one  over  the 
other.  Each  layer  seems  to  be  formed  of  lon- 
gitudinal fibres. 

In  each  nail  we  may  distinguish  three  parts, 
viz.  the  root,  the  body  or  middle,  and  the  ex- 
tremity. The  root  is  of  a soft,  thin,  and  white 
substance,  terminating  in  the  form  of  a cres- 
cent ; the  epidermis  adheres  very  strongly  to 
this  part ; the  body  of  the  nail  is  broader,  red- 
der, and  thicker,  and  the  extremity  is  of  still 
greater  firmness. 

The  nails  increase  from  their  roots,  and  not 
from  their  upper  extremity. 

Their  principal  use  is  to  cover  and  defend 
the  ends  of  the  fingers  and  toes  from  external 
injury. 

7.  Of  the  Hair. 

The  hairs,  which  from  their  being  general- 
ly known  do  not  seem  to  require  any  definition, 
arise  from  distinct  capsules  or  bulbs  seated  in 
the  cellular  membrane  under  the  skin.*  Some 

* Malpighi,  and  after  him  the  celebrated  Ruysch,  supposed 
the  hairs  to  be  continuations  of  nerves,  being  of  opinion  that 
they  originated  from  the  papillae  of  the  skin,  which  they  consi- 
dered as  nervous ; and  as  a corroborating  proof  of  what  they 
advanced,  they  argued  the  pain  we  feel  in  plucking  them  out ; 
but  later  anatomists  seem  to  have  rejected  this  doctrine  and  con- 
sider the  hairs  as  particular  bodies,  notarising  from  the  papillae 
(for  in  the  parts  where  the  papillae  abound  most  there  are  no 
hairs,)  but  from  bulbs  or  capsules,  which  are  peculiar  to  them. 


168 


Of  the  Integuments , &c. 


of  these  bulbs  inclose  several  hairs.  They 
may  be  observed  at  the  roots  of  the  hairs 
which  form  the  beard  or  whiskers  of  a cat. 

The  hairs,  like  the  nails,  grow  only  from 
below  by  a regular  propulsion  from  their  root, 
where  they  receive  their  nourishment.  Their 
bulbs,  when  viewed  with  a microscope,  are 
found  to  be  of  various  shapes,  In  the  head 
and  scrotum  they  are  roundish  ; in  the  eye- 
brows they  are  oval ; in  the  other  parts  of  the 
body  they  are  nearly  of  a cylindrical  shape. 
Each  bulb  seems  to  consist  of  two  membranes, 
between  which  there  is  a certain  quantity  of 
moisture.  Within  the  bulb  the  hair  separates 
into  three  or  four  fibrillae ; the  bodies  of  the 
hairs,  which  are  the  parts  without  the  skin, 
vary  in  softness  and  colour  according  to  the 

difference  of  climate,  age,  or  temperament  of 

* 

Their  general  use  in  the  body  does  not  seem 
to  be  absolutely  determined ; but  hairs  in  par- 
ticular parts,  as  on  the  eye-brows  and  eye-lids, 
are  destined  for  particular  uses,  which  will  be 
mentioned  when  those  parts  are  described. 

8.  Of  the  Cellular  Membrane  and  Fat. 

The  cellular  membrane  is  found  to  invest 
the  most  minute  fibres  we  are  able  to  trace  ; so 
that  by  modern  physiologists,  it  is  very  pro- 

* The  hairs  differ  likewise  from  each  other,  and  may  not  be 
improperly  divided  into  two  classes  ; one  of  which  may  include 
the  hair  of  the  head,  chin,  pubes,  and  axillae  ; and  the  other,  the 
softer  hairs,  which  are  to  be  observed  almost  every  where  on 
the  surface  of  the  body. 


Of  the  Integuments , &c,  169 

perly  considered  as  the  universal  connecting 
medium  of  every  part  of  the  body. 

It  is  composed  of  an  infinite  number  of  mi- 
nute cells  united  together,  and  communicating 
With  each  other.  The  two  diseases  peculiar 
to  this  membrane  are  proofs  of  such  a commu- 
nication ; for  in  the  emphysema  all  its  cells  are 
filled  with  air,  and  in  the  anasarca  they  are 
universally  distended  with  water.  Besides  these 
proofs  of  communication  from  disease,  a fa- 
miliar instance  of  it  may  be  observed  among 
butchers,  who  usually  puncture  this  membrane, 
and  by  inflating  it  with  air  add  to  the  good  ap- 
pearance of  their  meat. 

The  cells  of  this  membrane  serve  as  re- 
servoirs to  the  oily  part  of  the  blood  or  Fat, 
which  seems  to  be  deposited  in  them,  either 
by  transudation  through  the  coats  of  the  ar- 
teries, that  ramify  through  these  cells,  or  by 
particular  vessels,  continued  from  the  ends  of 
arteries.  These  cells  are  not  of  a glandular 
structure,  as  Malpighi  and  others  after  him 
have  supposed.  The  fat  is  absorbed  and  car- 
ried back  into  the  system  by  the  lymphatics. 
The  great  waste  of  it  in  many  diseases,  par- 
ticularly in  the  consumption,  is  a sufficient 
proof  that  such  an  absorption  takes  place. 

The  fulness  and  size  of  the  body  are  in  a 
great  measure  proportioned  to  the  quantity  of 
fat  contained  in  the  cells  of  this  membrane. 

In  the  living  body  it  seems  to  be  a fluid  oil, 
which  concretes  after  death.  In  graminivo- 
rous animals,  it  is  found  to  be  of  a firmer  con- 
sistence than  in  man. 


Y 


170 


Of  the  Muscles. 


The  fat  is  not  confined  to  the  skin  alone, 
being  met  with  every  where  in  the  interstices 
of  muscles,  in  the  omentum,  about  the  kid- 
neys, at  the  basis  of  the  heart,  in  the  orbits, 
&c. 

The  chief  uses  of  the  fat  seem  to  be  to 
afford  moisture  to  all  the  parts  with  which  it 
is  connected ; to  facilitate  the  action  of  the 
muscles  ; and  to  add  to  the  beauty  of  the  body, 
by  making  it  every  where  smooth  and  equal. 

Sect.  II.  Of  the  Muscles. 


The  muscles  are  the  organs  of  motion.  The 
parts  that  are  usually  included  under  this  name 
consist  of  distinct  portions  of  flesh,  suscepti- 
ble of  contraction  and  relaxation  ; the  motions 
of  which  in  a natural  and  healthy  state,  are 
subject  to  the  will,  and  for  this  reason  they 
are  called  voluntary  muscles.  But  besides 
these,  there  are  other  parts  of  the  body  that 
owe  their  power  of  contraction  to  their  mus- 
cular fibres  ; thus  the  heart  is  of  a muscular 
texture,  forming  what  is  called  a hollow  mus- 
cle ; and  the  urinary  bladder,  stomach,  intes- 
tines, 8tc.  are  enabled  to  act  upon  their  con- 
tents, merely  because  they  are  provided  with 
muscular  fibres.  These  are  called  involuntary 
muscles,  because  their  motions  are  not  depen- 
dent on  the  will.  The  muscles  of  respiration, 
being  in  some  measure  influenced  by  the  will, 
are  said  to  have  a mixed  motion. 


Of  the  Muscles. 


171 


The  names  by  which  the  voluntary  muscles 
are  distinguished,  are  founded  on  their  size, 
figure,  situation,  use,  or  the  arrangement  of 
their  fibres,  or  their  origin  and  insertion.  But 
besides  these  particular  distinctions,  there  are 
certain  general  ones  that  require  to  be  noticed. 

Thus,  if  the  fibres  of  a muscle  are  placed 
parallel  to  each  other  in  a straight  direction, 
they  form  whftt  are  styled  a rectilinear  muscle  ; 
if  the  fibres  cross  and  intersect  each  other,  they 
constitute  a compound  muscle  ; a radiated  one, 
if  the  fibres  are  disposed  in  the  manner  of 
rays;  or  a pcnniform  muscle,  if,  like  the  plume 
of  a pen,  they  are  placed  obliquely  with  re- 
spect to  the  tendon. 

Muscles  that  act  in  opposition  to  each  other, 
are  called  antagonists ; thus  every  extensor 
muscle  has  a flexor  for  its  antagonist,  and  vice 
versa . Muscles  that  concur  in  the  same  ac- 
tion are  styled  congeneres. 

The  muscles  being  attached  to  the  bones, 
the  latter  may  be  considered  as  levers  that  are 
moved  in  different  directions  by  the  contrac- 
tion of  those  organs. 

The  end  of  a muscle  which  adheres  to  the 
most  fixed  part  is  usually  called  the  origin , 
and  that  which  adheres  to  the  more  moveable 
part,  the  insertion , of  the  muscle. 

In  every  muscle  we  may  distinguish  two 
kinds  of  fibres ; the  one  soft,  of  a red  colour, 
sensible  and  irritable,  called  fleshy  fibres  ; the 
other  of  a firmer  texture,  of  a white  glisten- 
ing colour,  insensible,  without  irritability  or 
the  power  of  contracting,  and  named  tendinous 


172 


Of  the  Muscles. 


fibres.  They  are  occasionally  intermixed  ; but 
the  fleshy  fibres  generally  prevail  in  the  belly 
or  middle  part  of  a muscle,  and  the  tendi- 
nous ones  in  the  extremities.  If  these  tendi- 
nous fibres  are  formed  into  a round  slender 
chord,  they  form  what  is  called  the  tendon  of 
the  muscle  ; on  the  other  hand,  if  they  are 
spread  into  a broad  flat  surface,  the  extremity 
of  the  muscle  is  styled  aponeurosis. 

The  tendons  of  many  muscles,  especially 
when  they  are  long  and  exposed  to  pressure  or 
friction  in  the  grooves  formed  for  them  in  the 
bones,  are  surrounded  by  a tendinous  sheath 
or  fascia,  in  which  we  sometimes  find  a small 
mucous  sac  or  bursa  mucosa , which  obviates 
any  inconvenience  from  friction.  Sometimes 
we  find  whole  muscles,  and  even  several  mus- 
cles, covered  by  a fascia  of  the  same  kind, 
that  affords  origin  to  many  of  their  fibres,  dip- 
ping down  between  them,  adhering  to  the 
ridges  of  bones,  and  thus  preventing  them 
from  swelling  too  much  when  in  action.  The 
most  remarkable  instance  of  such  a covering 
is  the  fascia  lata  of  the  thigh. 

Each  muscle  is  inclosed  by  a thin  covering 
of  cellular  membrane,  which  has  been  some- 
times improperly  considered  as  peculiar  to  the 
muscles,  and  described  under  the  name  of pro- 
pria membrana  musculosa.  This  cellular  co- 
vering dips  down  into  the  substance  of  the 
muscle,  connecting  and  surrounding  the  most 
minute  fibres  we  are  able  to  demonstrate,  and 
affording  a support  to  their  vessels  and  nerves. 

Lieuwenhoeck  fancied  he  had  discovered,  by 


Of  the  Muscles . 


17$ 


means  of  his  microscope,  the  ultimate  division 
of  a muscle,  and  that  he  could  point  out  the  sim- 
ple fibre,  which  appeared  to  him  to  be  an  hun- 
dred times  less  than  a hair ; but  he  was  after- 
wards convinced  how  much  he  was  mistaken 
on  this  subject,  and  candidly  acknowledged, 
that  what  he  had  taken  for  a simple  fibre  was 
in  fact  a bundle  of  fibres. 

It  is  easy  to  observe  several  of  these  fasci- 
culi or  bundles  in  a piece  of  beef,  in  which, 
from  the  coarseness  of  its  texture,  they  are 
very  evident. 

The  red  colour  which  so  particularly  distin- 
guishes the  muscular  or  fleshy  parts  of  ani- 
mals, is  owing  to  an  infinite  number  of  blood- 
vessels that  are  dispersed  through  their  sub- 
stance. When  we  macerate  the  fibres  of  a 
muscle  in  water,  it  becomes  of  a white  colour 
like  all  other  parts  of  the  body  divested  of 
their  blood.  The  blood-vessels  are  accompa- 
nied by  nerves,  and  they  are  both  distributed  in 
such  abundance  to  these  parts,  that  in  endea- 
vouring to  trace  the  course  of  the  blood-ves- 
sels in  a muscle,  it  would  appear  to  be  formed 
altogether  by  their  ramifications  ; and  in  an 
attempt  to  follow  the  branches  of  its  nerves, 
they  would  be  found  to  be  equal  in  propor- 
tion. 

If  a muscle  is  pricked  or  irritated,  it  im- 
mediately contracts.  This  is  called  its  irrita- 
ble principle  ; and  this  irritability  is  to  be  con- 
sidered as  the  characteristic  of  muscular  fibres, 
and  may  serve  to  prove  their  existence  in  parts 
that  are  too  minute  to  be  examined  by  the  eye. 


174 


Of  the  Muscles. 


This  power,  which  disposes  the  muscles  to 
contract  when  stimulated,  independent  of  the 
will,  is  supposed  to  be  inherent  in  them ; and 
is  therefore  named  vis  insita.  This  property 
is  not  to  be  confounded  with  elasticity,  which 
the  membranes  and  other  parts  of  the  body 
possess  in  a greater  or  less  degree  in  common 
with  the  muscles ; nor  with  sensibility,  for 
the  heart,  though  the  most  irritable,  seems  to 
be  the  least  sensible  of  any  of  the  muscular 
parts  of  the  body. 

After  a muscular  fibre  has  contracted,  it 
soon  returns  to  a state  of  relaxation,  till  it 
is  excited  afresh,  and  then  it  contracts  and  re- 
laxes again.  We  may  likewise  produce  such 
a contraction,  by  irritating  the  nerve  leading 
to  a muscle,  although  the  nerve  itself  is  not 
affected. 

This  principle  is  found  to  be  greater  in 
small  than  in  large,  and  in  young  than  in  old, 
animals. 

In  the  voluntary  muscles  these  effects  of  con- 
traction and  relaxation  of  the  fleshy  fibres  are 
produced  in  obedience  to  the  will,  by  what  may 
be  called  the  vis  nervosa , a property  that  is 
tiot  to  be  confounded  with  the  vis  insita.  As 
the  existence  of  a vis  insita  different  from  a 
vis  nervea , was  the  doctrine  taught  by  Doctor 
Haller  in  his  JElem.  Phys.  but  is  at  present 
called  in  question  by  several,  particularly  Doc- 
tor Monro,  we  think  it  necessary  to  give  a few 
objections,  as  stated  in  his  Observations  on 
the  Nervous  System : 


Of  the  Muscles. 


175 


The  chief  experiment  (says  the  Doctor) 
which  seems  to  have  led  Dr.  Haller  to  this 
opinion,  is  the  well  known  one,  that  the  heart 
and  other  muscles,  after  being  detached  from 
the  brain,  continue  to  act  spontaneously,  or 
by  stimuli  may  be  roused  into  action  for  a con- 
siderable length  of  time  ; and  when  it  cannot 
be  alleged,  says  Dr.  Haller,  that  the  nervous 
fluid  is  by  the  mind,  or  otherwise,  impelled 
into  the  muscle. 

“ That  in  this  instance,  we  cannot  compre- 
hend by  what  power  the  nervous  fluid  or  ener- 
gy can  be  put  in  motion,  must  perhaps  be 
granted:  But  has  Dr.  Haller  given  a better 
explanation  of  the  manner  in  which  his  sup- 
posed vis  insita  becomes  active  ? 

“ If  it  be  as  difficult  to  point  out  the  cause 
of  the  action  of  the  vis  insita  as  that  of  the 
action  of  the  vis  nervea,  the  admission  of 
that  new  power,  instead  of  relieving,  would 
add  to  our  perplexity. 

“We  should  then  have  admitted,  that  two 
causes  of  a different  nature  were  capable  of 
producing  exactly  the  same  effect;  which  is 
not  in  general  agreeable  to  the  laws  of  nature. 

“We  should  find  other  consequences  arise 
from  such  an  hypothesis,  which  tend  to  weak- 
en the  credibility  of  it.  For  instance,  if  in  a 
sound  animal  the  vis  nervea  alone  produces 
the  contraction  of  the  muscles,  we  will  ask 
what  purpose  the  vis  insita  serves  ? If  both 
operate,  are  we  to  suppose  that  the  vis  nervea, 
impelled  by  the  mind  or  living  principle,  gives 
the  order,  which  the  vis  insita  executes,  and 


176 


Of  the  Muscles. 


that  the  nerves  are  the  internuntii ; and  so  ad- 
mit two  wise  agents  employed  in  every  the  most 
simple  action  ? But  instead  of  speculating  far- 
ther, let  us  learn  the  effect  of  experiments, 
and  endeavour  from  these  to  draw  plain  conclu- 
sions. 

“ 1.  When  I poured  a solution  of  opium  in 
water  under  the  skin  of  the  leg  of  a frog,  the 
muscles,  to  the  surface  of  which  it  was  appli- 
ed, were  very  soon  deprived  of  the  power  of 
contraction.  In  like  manner,  when  I poured 
this  solution  into  the  cavity  of  the  heart,  by 
opening  the  vena  cava,  the  heart  was  almost 
instantly  deprived  of  its  power  of  motion,  whe- 
ther the  experiment  was  performed  on  it  fixed 
in  its  place,  or  cut  out  of  the  body. 

u 2.  I opened  the  thorax  of  a living  frog; 
and  then  tied  or  cut  its  aorta,  so  as  to  put  a 
stop  to  the  circulation  of  its  blood. 

“ I then  opened  the  vena  cava,  and  poured 
the  solution  of  opium  into  the  heart ; and 
found,  not  only  that  this  organ  was  instantly 
deprived  of  its  powers  of  action,  but  that  in  a 
few  minutes  the  most  distant  muscles  of  the 
limbs  were  extremely  weakened.  Yet  this 
weakness  was  not  owing  to  the  want  of  circu- 
lation, for  the  frog  could  jump  about  for  more 
than  an  hour  after  the  heart  was  cut  out. 

“ In  the  first  of  these  two  experiments,  we 
observed  the  supposed  vis  insita  destroyed  by 
the  opium;  in  the  latter,  the  vis  nervea;  for  it 
is  evident  that  the  limbs  were  affected  by  the 
sympathy  of  the  brain,  and  of  the  nervous 


Of  the  Muscles . 177 

system  in  general,  with  the  nerves  of  the 
heart. 

3.  When  the  nerve  of  any  muscle  is  first 
divided  by  a transverse  section,  and  then 
burnt  with  a hot  iron,  or  punctured  with  a nee- 
dle, the  muscle  in  which  it  terminates  con- 
tracts violently,  exactly  in  the  same  manner  as 
when  the  irritation  is  applied  to  the  fibres  of 
the  muscle.  But  when  the  hot  iron,  or  nee- 
dle, is  confined  to  the  nerve,  Dr.  Haller  him- 
self must  have  admitted,  that  the  vis  nervea, 
and  not  the  vis  insita,  was  excited.  But  here 
I would  ask  two  questions. 

“ First,  Whether  we  do  not  as  well  under- 
stand how  the  vis  nervea  is  excited  when  irri- 
tation is  applied  to  the  muscle  as  when  it  is  ap- 
plied to  the  trunk  of  the  nerve,  the  impelling 
power  of  the  mind  seeming  to  be  equally 
wanting  in  both  cases  ? 

^ Secondly,  If  it  appears  that  irritation  ap- 
plied to  the  trunk  of  a nerve  excites  the  vis 
nervea,  why  should  we  doubt  that  it  can  equal- 
ly well  excite  it  when  applied  to  the  small  and 
very  sensible  branches  and  terminations  of  the 
nerve  in  the  muscle  ? 

“ As,  therefore,  it  appears  that  the  suppos- 
ed vis  insita  is  destroyed  or  excited  by  the 
same  means  as  the  vis  nervea  ; nay,  that  when, 
by  the  application  of  opium  to  the  heart  of  a 
frog,  after  the  aorta  is  cut  and  the  circulation 
interrupted,  we  have  destroyed  the  vis  insita, 
the  vis  nervea  is  so  much  extinguished,  that 
the  animal  cannot  act  with  the  distant  muscles 

Z 


178 


Of  the  Muscles . 


of  the  limb;  and  that  these  afterward  grow 
very  torpid,  or  lose  mucu  of  their  supposed 
vis  insita  ; it  seems  clearly  to  follow,  that  there 
is  no  just  ground  for  supposing  that  any  other 
principle  produces  the  contraction  of  a mus- 
cle.” 

The  vis  nervosa , or  operation  of  the  mind, 
if  we  may  so  call  it,  by  which  a muscle  is 
brought  into  contraction,  is  not  inherent  in  the 
muscle  like  the  vis  insita  ; neither  is  it  perpe- 
tual, like  this  latter  property.  After  long  con- 
tinued or  violent  exercise,  for  example,  the  vo- 
luntary muscles  become  painful,  and  at  length 
incapable  of  further  action  ; whereas  the  heart 
and  other  involuntary  muscles,  the  motions  of 
which  depend  solely  on  the  vis  insita , continue 
through  life  in  a constant  state  of  action,  with- 
out any  inconvenience  or  waste  of  this  inherent 
principle. 

The  action  of  the  vis  nervosa  on  the  volun- 
tary muscles,  constitutes  what  is  called  mus- 
cular motion  ; a subject  that  has  given  rise  to 
a variety  of  hypotheses,  many  of  them  inge- 
nious, but  none  of  them  satisfactory. 

Borelli  and  some  others  have  undertaken  to 
explain  the  cause  of  contraction,  by  suppos- 
ing that  every  muscular  fibre  forms  as  it  were 
a chain  of  very  minute  bladders,  while  the 
nerves  which  are  distributed  through  the  mus- 
cle, bring  with  them  a supply  of  animal  spi- 
rits, which  at  our  will  fill  these  bladders,  and 
by  increasing  their  diameter  in  width,  shorten 
them,  and  of  course  the  whole  fibre. 


Of  the  Muscles. 


179 


Borelli  supposes  these  bladders  to  be  of  a 
rhomboidal  shape ; Bernouilli  on  the  other 
hand  contends  that  they  are  oval.  Our  coun- 
tryman, Cowper,  fancied  he  had  filled  them 
witn  mercury  ; the  cause  of  this  mistake  was 
probably  owing  to  the  mercury’s  insinuating 
itself  into  some  of  the  lymphatic  vessels.  The 
late  ingenious  Mr.  Elliot  undertook  to  account 
for  the  phenomena  of  muscular  motion  on  prin- 
ciples very  different  from  those  just  now  men- 
tioned. He  supposed  that  a dephlogisticated 
state  of  the  blood  is  requisite  for  muscular  ac- 
tion, and  that  a communication  of  phlogiston  to 
the  blood  is  a necessary  effect  of  such  action. 

We  know  that  the  muscular  fibre  is  shorten- 
ed, and  that  the  muscle  itself  swells  when  in 
action  ; but  how  these  phenomena  are  produc- 
ed, we  are  unable  to  determine.  We  likewise 
know  that  the  nerves  are  essential  to  muscu- 
lar motion ; for  upon  dividing  or  making  a li- 
gature round  the  nerve  leading  to  a muscle, 
the  latter  becomes  incapable  of  motion.  A li- 
gature made  on  the  artery  of  a muscle  pro- 
duces a similar  effect;  a proof  this,  that  a re- 
gular supply  of  blood  is  also  equally  necessa- 
ry to  muscular  motion.  The  cause  of  palsy 
is  usually  not  to  be  sought  for  in  the  muscle 
affected,  but  in  the  nerve  leading  to  that  mus- 
cle, or  in  that  part  of  the  brain  or  spinal  mar- 
row from  which  the  nerve  derives  its  origin. 


180 


Of  the  Muscles. 


Of  the  particular  Muscles. 

As  the  enumeration  and  description  of  the 
particular  muscles  must  be  dry  and  unenter- 
taining to  the  generality  of  readers,  yet  can- 
not be  altogether  omitted  in  a work  of  this 
nature,  it  appeared  eligible  to  throw  this  part 
of  the  subject  into  the  form  of  a table  ; in 
which  the  name,  origin,  insertion,  and  princi- 
pal use  of  each  muscle,  will  be  found  describ- 
ed in  few  words,  and  occasionally  its  etymolo- 
gy when  it  is  of  Greek  derivation  or  difficult 
to  be  understood. 


A TABLE  of  the  MUSCLES,  arranged  according  to  their  Situation. 


Of  the  Muscles. 


181 


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the  dentes  incisores. 


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(*)  This  muscle  is  in  a great  measure  if  not  wholly,  formed  by  the  buccinator,  rygomatici,  depre38ore9,  and  other  muscles  that 
move  the  lips.  Its  fibres  surround  the  mouth  like  a ring. 


186 


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(*)  Some  of  its  fibres  likewise  have  their  origin  from  a strong  fascia  that  covers  the  muscle  and  adheres  to  the  bone  round  the 
whole  circumference  of  its  origin.  When  we  remove  this  covering,  we  find  the  muscle  of  a semicircular  shape  with  its  res,  con 
verging  and  forming  a strong  middle  tendon. 

(fj  So  called  from  its  use  in  chewing,  its  derivation  being  from  /uurinoi ««>  manduco,  “ to  eat.” 


Name.  Origin.  Insertion.  JJse- 

Pterygoideus  in-  From  the  inner  sur-  Into  the  lower  jaw  To  raise  the  lower 
ternus.  face  of  the  outer  on  its  inner  side  jaw  and  draw  it  a 

wing  of  the  ptery-  and  near  its  angle.  little  to  one  side, 
goid  process  of  the 


Of  the  Muscles . 


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( ^ ' 'u-S  ^iaPPens  the  muscle  acts  singly.  When  both  act,  the  jaw  is  brought  horizontally  forwards. 

(f;  This  broad  and  thin  muscular  expansion,  which  is  situated  immediately  under  the  common  integuments,  is  by  Winslow  named 
muscu  us  cutaneus.  Ga4en  gave  it  the  name  of  wx.r v<r/t«  pwafa  ( Phtysma-myoidcs ) ; the 'etymology  of  which  is  from  ^Aa-ruty^  dilatatio 
unci  w,  musculus , and  forma . * 


the  pectoral,  del.  merits  of  the  cheek.  downwards;  and 
toid,  and  trapezius  when  the  mouth  is 

muscles.  shut,  to  draw  all 

that  part  of  the  skin 


188 


Of  the  Muscles. 


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niche,  and  some- 

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(f)  This  muscle  does  not  always  arise  from  the  coracoid  process,  it  seems  to  have  been  improperly  named  coraso-hyoidss  by  Douglae 
and  Albinus.  Winslow  calls  it  omo-byoideus,  on  account  of  its  general  origin  from  the  scapula. 


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(*)  From  Sis  yw?  (biventer,)  because  it  has  two  fleshy  bellies  with  a middle  tendon.  Thistendon  passes  through  the  stylo-hyoideus. 
(t)  In  some  subjects  we  meet  with  another  muscle,  which  from  its  having  nearly  the  same  origin,  insertion,  and  use  as  this,  has  bee« 
named  stylo-hyoideus  alter. 

($)  So  named  from  its  arising  near  the  dentes  molares  (nur.ai,)  and  its  being  inserted  into  the  os  hyoides. 

(§)  From  yivoow,  mentum,  the  “ chin-” 


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Name.  Origin.  Insertion.  Use. 

hyoides,  and  from  formis  of  the  occi-  upwards,  and  to 

the  ligament  that  pita'  bone,  about  compress  thelatter. 

unites  it  with  the  its  middle  and  be- 
thyroid  cartilage.  fore  the  great  fo- 


194 


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the  transverse  pro-  stylo  mastoid  fora- 
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196  Of  the  Muscles.  . 


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of  the  eight  infe-  (*),ossapubis(f),  port  the  viscera, 

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Of  the  Muscles. 


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Name.  Origin.  Insertion.  Xjst. 

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lumhalis. 

f Ac  flic  upper  part  of  this  muscle  a broad  thin  layer  of  fleshy  fibres  is  found  crossing,  and  intimately  adhering  to  it.  This  portion, 
which  is  ilc3cribcd  by  Albinos,  under  the  name  of  transversals  cervicis,  may  very  properly  be  considered  as  an  appendage  to  the  lougissi 
mus  dursi.  It  arises  from  the  transverse  processes  of  the  five  or  six  superior  dorsal  vertebra;,  and.  is  inserted  into  the  transverse  processes  of 


Nam*  Origin.  Insertion.  Use. 

1 6.  Spinalis  dorsi.  From  the  spinous  Into  the  spinous  pro-  To  extend  the  verte- 
processes  of  the  up-  cesses  of  the  nine  bra% 
permost  lumbar  superiordorsal  ver- 

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('5  These  muscles  are  to  be  found  only  in  the  neck  and  loins  ; which  have  been  described,  as  the  inter-transvtrsales  dorsi  being  rather 
small  tendons  than  muscles. 

■ + ) This  and  the  fallowing  pair  of  muscles  derive  their  name  of  psoas  from  +•«.  Iambus,  on  account  of  their  situation  at  the  anterior  part 
of  the  loins. 


Name.  Origin.  Insertion.  Use. 

3.  Iliacus  interims.  From  the  inner  lip,  In  common  with  the  To  assist  the  psoas 
hollow  part,  and  psoas  magnus.  magnus. 

edge  of  the  os 


Of  the  Muscles. 


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Name.  Origin.  Insertion.  Use. 

CoracO-brachia-  From  the  coracoid  Into  the  middle  and  To  roll  the  arm  for- 

lis  (*).  process  of  the  sea-  inner  side  of  the  wards  andupwards. 

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(•)  This  muscle  affords  a passage  to  the  musculo-cutaneous  nerve- 


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that  bone. 


212 


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230 


Of  the  Muscles. 


EXPLANATION  of  PLATES  XXIII.  and 

XXIV. 

Plate  XXIII. 

Fig.  1-  The  Muscles  immediately  under 
the  common  teguments  on  the  anterior  part  of 
the  body  are  represented  on  the  right  side  ; 
and  on  the  left  side  the  Muscles  are  seen 
which  come  in  view  when  the  exterior  ones 
are  taken  away. 

A,  The  frontal  muscle.  B,  The  tendinous 
aponeurosis  which  joins  it  to  the  occipital; 
hence  both  named  occipitofrontalis.  C,  Attol- 
lens  aurem.  D,  The  ear.  E,  Anterior  au- 
ris.  F F,  Orbicularis  palpebrarum.  G,  Le- 
vator labii  superioris  alaeque  nasi.  H,  Leva- 
tor anguli  oris.  I,  Zygomaticus  minor.  K, 
Zygomaticus  major.  L,  Masseter.  M,  Or- 
bicularis oris.  N,  Depressor  labii  inferioris. 
O,  Depressor  anguli  oris.  P,  Buccinator. 
QQ,,  Platysma  myoides.  R R,  Sterno-cleido- 
“mastoidaeus.  S,  Part  of  the  trapezius.  T, 
Part  of  the  scaleni. 

Superior  Extremity — U,  Deltoides.  V, 
Pectoralis  major-  W,  Part  of  the  latissimus 
dorsi.  X X,  Biceps  flexor  cubiti.  Y Y,  Part 
of  the  brachialis  externus-  Z Z,  The  begin- 
ning of  the  tendinous  aponeurosis  (from  the 
biceps),  which  is  spread  over  the  muscles  of 


1 


5% 


Anatomy.  Piat-exxin 


Of  the  Muscles. 


231 


the  fore-arm.  a a,  Its  strong  tendon  inserted 
into  the  tubercle  of  the  radius,  b b,  Part  of 
the  brachialis  internus-  c,  Pronator  radii  te- 
res. d,  Flexor  carpi  radialis-  e,  Part  of  the 
flexor  carpi  ulnaris-  f,  Palmaris  longus.  g, 
Aponeurosis  palmaris*  3,  Palmaris  brevis.  1, 
Ligamentum  carpi  annulare.  2 2,  Abductor 
minimi  digiti.  h,  Supinator  radii  longus.  i, 
The  tendons  of  the  thumb-  k,  Abductor  pol- 
licis.  1,  Flexor  pollicis  longus.  m m,  The 
tendons  of  the  flexor  sublimis  perforatus, 
profundus  perforans,  and  lumbricales — The 
sheaths  are  entire  in  the  right  hand, — in  the 
left  cut  open  to  show  the  tendons  of  the  flex- 
or profundus  petforating  the  sublimis. 

Muscles  not  referred  to — in  the  left  supe- 
rior extremity — n,  Pectoralis  minor,  seu  ser- 
ratus  anticus  minor,  o,  The  two  heads  of 
(x  x)  the  biceps,  p,  Coraco-brachialis.  q q, 
The  long  head  of  the  triceps  extensor  cubiti. 
rr,  Teres  major-  ff,  Subscapularis.  1 1,  Ex- 
tensores  radiales.  u,  Supinator  brevis-  v, 
The  cut  extremity  of  the  pronator  teres,  w, 
Flexor  sublimis  perforatus.  x,  Part  of  the 
flexor  profundus,  y,  Flexor  pollicis  longus. 
z,  Part  of  the  flexor  pollicis  brevis-  4,  Ab- 
ductor minimi  digiti.  5,  The  four  lumbri- 
cales. 

Trunk. — 6,  Serrated  extremities  of  the  ser- 
ratus  anticus  major-  7 7,  Obliquus  externus 
abdominis.  8 8,  The  lmea  alba-  9,  The  um- 
bilicus. 10,  Pyramidalis.  11  11,  The  sper- 
matic cord.  On  the  left  side  it  is  covered  by 


232 


Of  the  Muscles , 


the  cremaster.  12  12,  Rectus  abdominis.  13, 
Obliquus  internus-  14  14,  he.  Intercostal 
muscles. 

Inferior  Extremities — aa , The  graci- 
lis. b b , Parts  of  the  triceps,  c c,  Pectialis. 
d d , Psoas  magnus-  e e,  Iliacus  internus.  yj 
Part  of  the  glutseus  medius-  g.  Part  of  the 
glutseus  minimus,  /z,  Cut  extremity  of  the 
rectus  cruris,  i z,  Vastus  externus,  k , Ten- 
don of  the  rectus  cruris.  / /,  Vastus  internus. 
* Sartorius  muscle.  * * Fleshy  origin  of  the 
tensor  vaginas  faemoris  or  membranosus.  Its 
tendinous  aponeurosis  covers  (z)  the  vastus 
externus  in  the  right  side,  in  m,  Patella,  n n, 
Ligament  or  tendon  from  it  to  the  tibia,  o, 
Rectus  cruris.  />,  Crurasus.  q q,  The  tibia. 
r r,  Part  of  the  Gemellus  or  gastrocnemius  ex- 
ternus.* ///,  Part  of  the  soleus  or  gastroc- 
nemius internus.  £,  Tibialis  anticus.  zz,  Ti- 
bialis posticus,  v v,  Peronasi  muscles,  w w, 
Extensor  longus  digitorum  pedis,  x x,  Ex- 
tensor longus  pollicis  pedis-  y,  Abductor  pol- 
licis  pedis. 

Fig-  2-  The  Muscles,  Glands,  btc.  of  the 
Left  Side  of  the  face  and  neck,  after  the 
common  Teguments  and  Platysma  myoides 
have  been  taken  off. 

a,  The  frontal  muscle,  b,  Temporalis  and 
temporal  artery,  c,  Orbicularis  palpebrarum, 
d,  Levator  labii  superioris  alasque  nasi,  e, 
Levator  anguli  oris,  f,  Zygomaticus.  g,  De- 
pressor labii  inferioris.  h,  Depressor  anguli 


233 


Of  the  Muscles. 

©ris.  i,  Buccinator,  k,  Masseter.  1 1,  Paro- 
tid gland-  m,  Its  duct-  n,  Sterno-cleido-mas- 
toidseus.  o,  Part  of  the  trapezius,  p,  Sterno- 
hyoidaeus.  q,  Sterno-thyroidaeus.  r,  Omo- 
hyoidaaus.  f,  Levator  scapulas-  1 1,  Scaleni. 
u,  Part  of  the  splenius. 

Fig.  3.  The  Muscles  of  the  Face  and  Neck 
in  view  after  the  exterior  ones  are  taken 
away- 

a a,  Corru gator  supercilii-  b,  Temporalis- 

c,  Tendon  of  the  levator  palpebras  superioris- 

d,  Tendon  of  the  orbicularis  palpebrarum,  e, 
Masseter.  f,  Buccinator,  g,  Levator  anguli 
oris-  h,  Depressor  labii  superioris  alasque  na- 
si. i,  Orbicularis  oris-  k,  Depressor  anguli 
oris.  1,  Muscles  of  the  os  hyoides-  m,  Ster- 
no-cleido-mastoidaeus. 

Fig.  4-  Some  of  the  Muscles  of  the  Os  Hy- 
oides and  Submaxillary  Gland. 

a,  Part  of  the  masseter  muscle-  b,  Poste- 
rior head  of  the  digrastic.  c,  Its  anterior 
head,  d d,  Sterno-hyoidaeus.  e,  Omo-hyoi- 
dams-  f,  Stylo-hyoidaeus.  g,  Submaxillary 
gland  in  situ. 

Fig.  5.  The  Submaxillary  Gland  and  Duct, 
a,  Musculus  mylo-hyoidaeus.  b,  Hyo-glos- 
sus.  c,  Submaxillary  gland  extra  situ,  d,  Its 
duct. 

Plate  XXIV. 

Fig.  1.  The  Muscles  immediately  under 
the  common  teguments  on  the  posterior  part 

G g 


234 


Of  the  Muscles. 


of  the  body,  are  represented  in  the  right  side;: 
and  on  the  left  side  the  Muscles  are  seen 
which  come  in  view  when  the  exterior  ones 
are  taken  away. 

Head. — A A,  Occipito-frontalis.  B,  Attol- 
lens  aurem.  C,  Part  of  the  orbicularis  palpe- 
brarum. D,  Masseter..  E,  Pterygoidaeus  in- 
ternusv 

Trunk. — Right  side.  FFF,  Trapezius  seu, 
cucullaris.  G G G G,  Latissimus  dorsi.  H, 
Part  of  the  obliquus  externus  abdominis. 

Trunk. — Left  side.  I,  Splenius-  K,  Part 
of  the  complexus.  Lr  Levator  scapulae.  M, 
Rhomboides.  N N,  Serratus  posticus  inferi- 
or. O,  Part  of  the  longissimus  dorsi.  P, 
Part  of  the  sacro-lumbalis.  Q,  Part  of  the 
semi-spinalis  dorsi.  R,  Part  of  the  serratus 
anticus  major.  S,  Part  of  the  obliquus  in- 
ternus  abdominis. 

Superior  Extremity. — Right  side-  Tt 
Deltoides.  U,  Triceps  extensor  cubiti-  V, 
Supinator  longus.  W W,  Extensores  carpi 
radialis  longior  and  brevior-  X X,  Extensor 
carpi  ulnaris.  Y Y,  Extensor  digitorum  com- 
munis. Z,  Abductor  indicis.  12  3,  Extern- 
sores  pollicis. 

Superior  Extremity. — Left  side,  a,  Su- 
pra spinatus.  b,  Infra-spinatus.  c,  Teres 
minor,  d,  Teres  major,  e,  Triceps  extensor 
cubiti.  f f,  Extensores  carpi  radiales.  g,  Su- 
pinator brevis,  h,  Indicator.  12  3,  Exten- 
sores pollicis.  i,  Abductor  minimi  digiti.  k, 
Interossei. 

Inferior  Extremity. — Right  side.  1,  Glu- 
trnus  maximus.  m,  Part  of  the  Glutseus  me- 


Of  the  Muscles. 


255 


dius.  n,  Tensor  vaginae  femoris.  o,  Graci- 
lis- p p,  Abductor  femoris  magnus.  q,  Part 
of  the  vastus  internus-  r,  Semimembrano- 
sus. s,  Semitendinosus-  t,  Long  head  of  the 
biceps  flexor  cruris,  u u,  Gastrocnemius  ex- 
ternus  seu  gemellus,  v,  Tendo  Achillis.  w, 
Soleus  seu  gastrocnemius  internus.  x x,  Pe- 
ronaeus  longus  and  br-evis.  y,  Tendons  of  the 
flexor  longus  digitorum  pedis  ; — and  under 
them  * flexor  brevis  digitorum  pedis-  z.,  Ab  • 
ductor  minimi  digiti  pedis. 

Inferior  Extremity. — -Left  side.  ?n,  n , 
o,  p , y,  r,  s,  v,  w w , x x,  y,  zr,  Point  the 
same  parts  as  in  the  right  side,  a , Pyrifor- 
mis.  b b,  Gemini,  c r,  Obturator  internus. 
r7,  Quadratus  femoris.  e,  Coccygaeus.  f The 
short  head  of  the  biceps  flexor  cruris-  g g, 
Plantaris.  h , Poplitaeus.  L Plexor  longus 
pollicis  pedis. 

Pig.  2.  The  Palm  of  the  'Left  Hand  after  the 

common  Teguments  are  removed,  to  .show 

the  Muscles  of  the  Fingers. 

a,  Tendon  of  the  flexor  carpi  radiaiis.  b, 
Tendon  of  the  flexor  carpi  ulnaris.  c,  Ten- 
dons of  the  flexor  sublimis  perforatus,  pro- 
fundus perforans  and  lumbri.cales.  d,  Ab- 
ductor pollicis.  e e,  Plexor  pollicis  'longus- 
f,  Flexor  pollicis  brevis,  g,  Palmaris  brevis- 
h,  Abductor  minimi  digiti.  i,  Ligamentum 
carpiannulare.  k,  A probe  put  under  the  ten- 
dons of  the  flexor  digitorum  sublimis ; which 
are  perforated  by  1,  the  flexor  digitorum  pro- 
fundus. m m m m,  Lumbricales.  n,  Abduc- 
tor jpollicis. 


236 


Of  the  Abdomen . 


Fig  3.  A Fore-view  of  the  foot  and  Tendons 
of  tne  Flexores  Digitorum. 

a,  Cut  extremity  of  the  tendo  Achillis.  by 
Upper  part  of  the  astragalus,  c,  Os  calcis. 

d,  Tendon  of  the  tibialis  anticus.  e,  Tendon 
of  the  extensor  poll icis  longus.  f,  Tendon  of 
the  peronaeus  brevis,  g,  Tendons  of  the  flex- 
or digitorum  longus,  with  the  nonus  Vesalii. 
h h,  The  whole  of  the  flexor  digitorum  bre- 
vis. 

Fig.  4.  Muscles  of  the  Anus. 

a a,  An  out  line  of  the  buttocks,  and  upper 
part  of  the  thighs,  b,  The  testes  contained 
in  the  scrotum,  c c,  Sphincter  ani.  d,  Anus, 

e,  Levator  ani.  f f,  Erector  penis,  g g,  Ac- 
celerator urinse.  h,  Corpus  cavernosum  ure- 
thrae. 

Fig.  5.  Muscles  of  the  Penis. 

a a,  b,  d,  e e,  f f,  h,  point  the  same  as  in 
fig.  4.  c,  Sphincter  ani.  gg,  Transversalis 
penis. 


Part  III.  OF  THE  ABDOMEN,  OR 
LOWER  BELLY. 

THE  abdomen  or  lower  belly,  extends  from 
the  lower  extremity  of  the  sternum,  or 
the  hollow,  usually  called  the  pit  of  the  sto- 
mach, and  more  properly  scrobiculus  cordis , to- 
the  lower  part  of  the  trunk- 


Of  the  Abdomen. 


237 


It  is  distinguished  into  three  divisions  call- 
ed regions ; of  tnese  the  upper  one,  which  is 
called  the  epigastric  region , begins  immediate- 
ly under  the  sternum,  and  extends  to  within 
two  fingers  breadth  of  the  navel,  where  the 
middle  or  umbilical  region  begins,  and  reaches 
to  the  same  distance  below  the  navel.  The 
third,  which  is  called  the  hypogastric , includes 
the  rest  of  the  abdomen,  as  far  as  the  os  pu- 
bis. 

Each  of  these  regions  is  subdivided  into 
three  others  ; two  of  which  compose  the  sides, 
and  the  other  the  middle  part  of  each  region. 

1 he  middle  part  of  the  upper  region  is  call- 
ed epigastrium , and  its  two  sides  hypochondria. 
The  middle  part  of  the  next  region  is  the  um- 
bilical region,  properly  so  called,  and  its  two 
sides  are  the  flanks,  or  iliac  regions.  Lastly, 
the  middle  part  of  the  lower  region  retains  the 
name  of  hypogastrium,  and  its  sides  are  call- 
ed inguina  or  groins.  The  back  part  of  the 
abdomen  bears  the  name  of  lumbar  region. 

These  are  the  divisions  of  the  lower  belly, 
which  are  necessary  to  be  held  in  remem- 
brance, as  they  frequently  occur  in  surgical 
and  anatomical  writing-  We  will  now  proceed 
to  examine  the  contents  of  the  abdomen  ; and 
after  having  pointed  out  the  names  and  ar- 
rangement of  the  several  viscera  contained  in 
it,  describe  each  of  them  separately- 

After  having  removed  the  skin,  adipose 
membrane,  and  abdominal  muscles,  we  disco- 
ver the  peritonaeum  or  membrane  that  enve- 
lopes all  the  viscera  of  the  lower  belly*  This 
being  opened,  the  first  part  that  presents  itself 


238 


Of  the  Abdomen. 


is  the  omentum  or  cawl,  floating  on  the  sur- 
face of  the  intestines,  which  are  likewise  seen 
every  where  loose  and  moist,  and  making  a 
great  number  of  circumvolutions  through  the 
whole  cavity  of  the  abdomen.  The  stomach 
is  placed  in  the  epigastrium,  and  under  the 
stomach  is  the  pancreas.  The  liver  fills  the 
right  hypochondrium,  and  the  spleen  is  situ- 
ated in  the  left-  The  kidneys  are  seen  about 
the  middle  of  the  lumbar  region,  and  the  uri- 
nary bladder  and  parts  of  generation  are  seat- 
ed in  the  lower  division  of  the  belly. 

Sect.  I.  Of  the  Peritoneum. 

The  peritonaeum  is  a strong  simple  mem- 
brane, by  which  all  the  viscera  of  the  abdo- 
men are  surrounded,  and  in  some  measure 
supported.  Many  anatomical  writers,  particu- 
larly Winslow,  have  described  it  as  being  com- 
posed of  two  distinct  membranous  laminae;  but 
their  description  seems  to  be  erroneous.  What 
perhaps  appeared  to  be  a second  lamina,  being 
found  to  be  simply  a cellular  coat,  which  sends 
off"  productions  to  the  blood-vessels  passing 
out  of  the  abdominal  cavity.  The  aorta  and 
vena  cava  likewise  derive  a covering  from  the 
same  membrane,  which  seems  to  be  a part  of 
the  cellular  membrane  we  have  already  de- 
scribed. 

The  peritonaeum,  by  its  productions  and  re- 
duplications, envelopes  the  greatest  part  of 
the  abdominal  viscera.  It  is  soft,  and  capable 
of  considerable  extension ; and  is  kept  smooth 
and  moist  by  a vapour  which  is  constantly  ex- 


23  S> 


Of  the  Abdomen. 

haling  from  its  inner  surface,  and  is  returned 
again  into  the  circulation  by  the  absorbents. 

This  moisture  not  only  contributes  to  the 
softness  of  the  peritonaeum,  but  prevents  the 
attrition,  and  other  ill  effects  which  would 
otherwise  probably  be  occasioned,  by  the  mo- 
tion of  the  viscera  upon  each  other. 

When  this  fluid  is  supplied  in  too  great  a 
quantity,  or  the  absorbents  become  incapable 
of  carrying  it  off,  it  accumulates,  and  consti- 
tutes an  ascites  or  dropsy  of  the  belly ; and 
when  by  any  means  the  exhalation  is  discon- 
tinued, the  peritonaeum  thickens,  becomes  dis- 
eased, and  the  viscera  are  sometimes  found 
adhering  to  each  other. 

The  peritonaeum  is  not  a very  vascular 
membrane.  In  a sound  state  it  seems  to  be 
endued  with  little  or  no  feeling,  and  the  nerves 
that  pass  through  it  appear  to  belong  to  the 
abdominal  muscles. 

Sect.  II.  Of  the  Omentum. 

The  omentum,  epiploon,  or  cawl,  is  a dou- 
ble membrane,  produced  from  the  peritonaeum. 
It  is  interlarded  with  fat,  and  adheres  to  the 
stomach,  spleen,  duodenum,  and  colon ; from 
thence  hanging  down  loose  and  floating  on  the 
surface  of  the  intestines-  Its  size  is  different 
in  different  subjects.  In  some  it  descends  as 
low  as  the  pelvis,  and  it  is  commonly  longer  at 
the  left  side  than  the  right. 

This  part,  the  situation  of  which  we  have 
just  now  described,  was  the  only  one  known 
to  the  ancients  under  the  name  of  epiploon ; 


240 


Of  the  Abdomen. 

but  at  present  we  distinguish  three  omenta, 
viz.  omentum  magnum  colico  gastricum , omen - 
turn  parvum  hepatico  gastricum, ind  omentum 
colicum.  Tney  all  agree  in  being  formed  of 
two  very  delieate  laminae,  separated  by  a thin 
layer  of  cellular  membrane. 

The  omentum  magnum  colico  gastricum,  of 
which  we  have  already  spoken,  derives  its  ar- 
teries from  the  splenic  and  hepatic.  Its  veins 
terminate  in  the  vena  portae.  Its  nerves,  which 
are  very  few,  come  from  the  splenic  and  he- 
patic plexus. 

The  omentum  parvum  hepatico  gastricum, 
abounds  less  with  fat  than  the  great  epiploon. 
It  begins  at  the  upper  part  of  the  duodenum, 
extends  along  the  lesser  curvature  of  the  sto- 
mach as  far  as  the  oesophagus,  and  terminates 
about  the  neck  of  the  gall-bladder,  and  behind 
the  left  ligament  of  the  liver,  so  that  it  covers 
the  lesser  lobe;  near  the  beginning  of  which 
we  may  observe  a small  opening,  first  describ- 
ed by  Winslow,  through  which  the  whole 
pouch  may  easily  be  distended  with  air.*  The 
vessels  of  the  omentum  parvum  are  derived 
chiefly  from  the  coronary  stomachic  arteries 
and  veins. 

The  omentum  colicum  begins  at  the  fore 
part  of  the  ccecum  and  right  side  of  the  colon. 
It  appears  as  a hollow  conical  appendage  to 
these  intestines,  and  usually  terminates  at  the 
back  of  the  omentum  magnum-  It  seems  to 

* This  membranous  bag-,  though  exceedingly  thin  and  trans- 
parent, is  found  capable  of  supporting  mercury,  thrown  into  it 
by  the  same  channel. 


Of  the  Abdomen.  241 

be  nothing  more  than  a membranous  coat  of 
the  cascum  and  colon,  assuming  a conical  shape 
when  distended  with  air. 

The  uses  of  the  omentum  are  not  yet  satis- 
factorily determined.  Perhaps  by  its  softness 
and  looseness  it  may  serve  to  prevent  those 
adhesions  of  the  abdominal  viscera,  which 
have  been  found  to  take  place  when  the  fat 
of  the  omentum  has  been  much  wasted.  Some 
authors  have  supposed,  that  it  assists  in  the 
preparation  of  bile  ; but  this  idea  is  founded 
merely  on  conjecture. 

Sect.  III.  Of  the  Stomach. 

The  stomach  is  a membranous  and  muscu- 
lar bag,  in  shape  not  unlike  a bag-pipe,  lying 
across  the  upper  part  of  the  abdomen,  and  in- 
clining rather  more  to  the  left  than  the  right 
side. 

It  has  two  orifices,  one  of  which  receives 
the  end  of  the  oesophagus,  and  is  called  the 
cardia , and  sometimes  the  left  and  upper  ori- 
fice of  the  stomach  ; though  its  situation  is  not 
much  higher  than  the  other,  which  is  styled 
the  right  and  inferior  orifice,  and  more  com- 
monly the  pylorus:  both  these  openings  are 
more  elevated  than  the  body  of  the  stomach. 

The  aliment  passes  down  the  oesophagus  in- 
to the  stomach  through  the  cardia,  and  after 
having  undergone  the  necessary  digestion, 
passes  out  at  the  pylorus  where  the  intesti- 
nal canal  commences. 

The  stomach  is  composed  of  four  tunics  or 
coats,  which  are  so  intimately  connected  toge- 

H h 


■242 


Of  the  Abdomen . 


ther  that  it  requires  no  little  dexterity  in  the 
anatomist  to  demonstrate  them.  The  exterior 
one  is  membranous,  being  derived  from  the 
peritonaeum. — The  second  is  a muscular  tu- 
nic, composed  of  fleshy  fibres  which  are  in  the 
greatest  number  about  the  two  orifices. — The 
third  is  called  the  nervous  coat,  and  within 
this  is  the  villous  or  velvet-like  coat  which 
composes  the  inside  of  the  stomach. 

The  two  last  coats  being  more  extensive 
than  the  two  first,  form  the  folds,  which  are 
observed  every  where  in  the  cavity  of  this 
viscus,  and  more  particularly  about  the  pylo- 
rus ; where  they  seem  to  impede  the  too  has- 
ty exclusion  of  the  aliment,  making  a conside- 
rable plait,  called  valvula  pylori. 

The  inner  coat  is  constantly  moistened  by  a 
mucus,  which  approaches  to  the  nature  of  the 
saliva,  and  is  called  the  gastric  juice  ; this  li- 
quor has  been  supposed  to  be  secreted  by  cer- 
tain minute  glands*  seated  in  the  nervous  tu- 
nic, whose  excretory  ducts  open  on  the  sur- 
face of  the  villous  coat. 

The  arteries  of  the  stomach  called  the  gas- 
tric arteries  are  principally  derived  from  the 
cseliac ; some  of  its  veins  pass  to  the  splenic, 
and  others  to  the  yena  portae ; and  its  nerves 
are  chiefly  from  the  eighth  pair  or  par  vagum. 

* Heister,  speaking  of  these  glands,  very  properly  says,  “ in 
porcis  facile,  in  homine  raro  observantur  for  although  many 
anatomical  writers  have  described  their  appearance  and  figure, 
yet  they  do  not  seem  to  have  been  hitherto  satisfactorily  demon- 
strated in  the  human  stomach  ; and  the  gastric  juice  is. now  more 
generally  believed  to  be  derived  from  the  exhalent  arteries  oi  the 
stomach. 


24S 


Of  the  Abdomen. 

The  account  given  of  the  tunics  of  the  sto- 
mach may  be  applied  to  the  whole  alimentary 
canal;  for  both  the  oesophagus  and  intestines 
are,  like  this  viscus,  composed  of  four  coats. 

Before  we  describe  the  course  of  the  ali- 
ment and  the  uses  of  the  stomach,  it  will  be 
necessary  to  speak  of  other  parts  which  assist 
in  the  process  of  digestion. 

Sect.  IV.  Of  the  Oesophagus. 

The  oesophagus  or  gullet  is  a membra- 
nous and  muscular  canal,  extending  from  the 
bottom  of  the  mouth  to  the  upper  orifice  of 
the  stomach. — Its  upper  part  where  the  ali- 
ment is  received  is  shaped  somewhat  like  a 
funnel,  and  is  called  the  pharynx.. 

From  hence  it  runs  down  close  to  the  bo- 
dies of  the  vertebrae  as  far  as  the  diaphragm, 
in  which  there  is  an  opening  through  which  it 
passes,  and  then  terminates  in  the  stomach 
about  the  eleventh  or  twelfth  vertebra  of  the 
back. 

The  oesophagus  is  plentifully  supplied  with 
arteries  from  the  external  carotid,  bronchial, 
and  superior  intercostal  arteries.;  its  veins 
empty  themselves  into  the  vena  azygos,  inter- 
nal jugular,  and  mammary  veins,  &c. 

Its  nerves  are  derived  chiefly  from  tire 
eighth  pair. 

We  likewise  meet  with  a mucus  in  the  oeso- 
phagus, which  every  where  lubricates  its  in- 
ner surface,  and  tends  to  assist  in  deglutition. 
—This  mucus  seems  to  be  secreted  by  very 
minute  glands,  like  the  mucus  in  other  parts 
of  the  alimentary  canal. 


244 


Of  the  Abdomen. 


Sect.  V.  Of  the  Intestines. 

The  intestines  form  a canal,  which  is  usu- 
ally six  times  longer  than  the  body  to  which 
it  belongs.  1 his  canal  extends  from  the  py- 
lorus, or  inferior  orifice  of  the  stomach,  to  the 
anus. 

It  will  be  easily  understood,  that  a part  of 
such  great  length  must  necessarily  make  many 
circumvolutions,  to  be  confined  with  so  many 
other  viscera  within  the  cavity  of  the  lower 
belly. 

Although  the  intestines  are  in  fact,  as  we 
have  observed,  only  one  long  and  extensive 
canal,  yet  different  parts  have  been  distin- 
guished by  different  names. 

The  intestines  are  first  distinguished  into 
two  parts,  one  of  which  begins  at  the  sto- 
mach, and  is  called  the  thin  or  small  intestines , 
from  the  small  size  of  the  canal,  when  com- 
pared with  the  other  part,  which  is  called  the 
large  intestines , and  includes  the  lower  portion 
of  the  canal  down  to  the  anus. 

Each  of  these  parts  has  its  subdivisions. — 
The  small  intestines  being  distinguished  into 
duodenum,  jejunum,  and  ilium,  and  the  larger 
portion  into  cascum,  colon,  and  rectum. 

The  small  intestines  fill  the  middle  and  fore 
parts  of  the  belly,  while  the  large  intestines 
fill  the  sides  and  both  the  upper  and  lower 
parts  of  the  cavity. 

The  duodenum,  which  is  the  first  of  the 
small  intestines,  is  so  called,  because  it  is 
about  12  inches  long.  It  begins  at  the  pylo- 


Of  the  Abdomen . 


245 


rus  and  terminates  in  the  jejunum,  which  is  a 
part  of  the  canal  observed  to  be  usually  more 
empty  than  the  other  intestines. — This  appear- 
ance gives  it  its  name,  and  likewise  serves  to 
point  out  where  it  begins. 

The  next  division  is  the  ilium,  which  of  it- 
self exceeds  the  united  length  of  the  duode- 
num and  jejunum,  and  has  received  its  name 
from  its  numerous  circumvolutions.  The 
large  circumvolution  of  the  ilium  covers  the 
first  of  the  large  intestines  called  the  cacumf 
which  seems  properly  to  belong  to  the  colon, 
being  a kind  of  pouch  of  about  four  fingers  in 
width,  and  nearly  of  the  same  length,  having 
exteriorly  a little  appendix,  called  appendix 
caci. 

The  csecum  is  placed  in  the  cavity  of  the 
os  ilium  on  the  right  side,  and  terminates  in 
the  colon,  which  is  the  largest  of  all  the  in- 
testines. 

This  intestine  ascends  by  the  right  kidney 
to  which  it  is  attached,  passes  under  the  hol- 
low part  of  the  liver,  and  the  bottom  of  the 
stomach,  to  the  spleen,  to  which  it  is  likewise 
secured,  as  it  is  also  to  the  left  kidney ; and 
from  thence  passes  down  towards  the  os  sa- 
crum, where,  from  its  straight  course,  the  ca- 
nal begins  to  take  the  name  of  rectum. 

There  are  three  ligamentous  bands  extend- 
ing through  the  whole  length  of  the  colon, 

* Anatomists  have  differed  with  respect  to  this  division  of  the 
intestines. — The  method  here  followed  is  now  generally  adopted  ; 
but  there  are  authors  who  allow  the  name  of  cacum  only  to  the 
little  appendix,  which  has  likewise  been  called  the  vermiform  ap- 
pendix, from  its  resemblance  to  a worm  in  size  and  length. 


246  Of  the  Abdomen. 

which,  by  being  shorter  than  its  two  inner 
coats,  serve  to  increase  the  plaits  on  the  in- 
ner surface  of  this  gut. 

The  anus  which  terminates  the  intestinum 
rectum,  is  furnished  with  three  muscles  ; one 
of  these  is  composed  of  circular  fibres,  and 
from  its  use  in  shutting  the  passage  of  the 
anus  is  called  sphincter  ani. 

The  other  two  are  the  levatores  ani , so  call- 
ed, because  they  elevate  the  anus  after  dejec- 
tion. When  these  by  palsy,  or  any  other  dis- 
ease lose  the  power  of  contracting,  the  anus 
prolapses ; and  when  the  sphincter  is  affected 
by  similar  causes,  the  faeces  are  voided  invo- 
luntarily. 

It  has  been  already  observed,  that  the  in- 
testinal canal  is  composed  of  four  tunics  ; but 
it  remains  to  be  remarked,  that  here,  as  in 
the  stomach,  the  two  inner  tunics  being  more 
extensive  than  the  other  two,  form  the  plaits 
which  are  to  be  seen  in  the  inner  surface  of 
the  intestines,  and  are  called  valvulce  conniven- 
tes. 

Some  authors  have  considered  these  plaits 
as  tending  to  retard  the  motion  of  the  faeces, 
in  order  to  afford  more  time  for  the  separa- 
tion of  the  chyle ; but  there  are  others  who 
attribute  to  them  a different  use : they  con- 
tend, that  these  valves,  by  being  naturally  in- 
clined downwards,  cannot  impede  the  descent 
of  the  faeces,  but  that  they  are  intended  to  pre- 
vent their  return  upwards. 

They  are  probably  destined  for  both  these 
uses ; for  although  these  folds  incline  to  their 
lower  side,  yet  the  inequalities  they  occasion 


247 


Of  the  Abdomen. 

in  the  canal  are  sufficient  to  retard,  in  some 
measure,  the  progressive  motion  of  the  faeces, 
and  to  afford  a greater  surface  for  the  absorp- 
tion of  chyle,  and  their  natural  position  seems 
to  oppose  itself  to  the  return  of  the  aliment. 

Besides  these  valvule  conniventes , there  is 
one  more  considerable  than  the  rest,  called  the 
valve  of  the  colon ; which  is  found  at  that  part 
of  the  canal  where  the  intestinum  ilium  is  join- 
ed to  the  colon.  This  valve  permits  the  ali- 
mentary pulp  to  pass  downwards,  but  serves 
to  prevent  its  return  upwards  ; and  it  is  by 
this  valve,  that  glysters  are  prevented  from 
passing  into  the  small  intestines.* 

Of  the  little  vermiform  appendix  of  the  cae- 
cum, it  will  be  sufficient  to  say,  that  its  uses 
have  never  yet  been  ascertained=  In  birds  we 
meet  with  two  of  these  appendices. 

The  intestines  are  lubricated  by  a constant 
supply  of  mucus,  which  is  probably  secreted 
by  very  minute  follicles. f This  mucus  pro- 
motes the  descent  of  the  alimentary  pulp,  and 
in  some  measure  defends  the  inner  surface  of 


* This  is  not  invariably  the  case,  for  the  contents  of  a gly- 
ster  have  been  found  not  only  to  reach  the  small  intestines,  but 
to  be  voided  at  the  mouth.  Such  instances,  however,  are  not 
common. 

f Some  writers  have  distinguished  these  glands  into  miliary, 
lenticular,  &c. — Brunner  and  Peyer  were  the  first  anatomists 
who  described  the  glands  of  the  intestines,  and  their  descrip- 
tions were  chiefly  taken  from  animals,  these  glandular  appear- 
ances not  seeming  to  have  been  hitherto  satisfactorily  pointed  out 
in  the  human  subject. — It  is  now  pretty  generally  believed,  that 
the  mucus  which  every  where  lubricates  the  alimentary  canal,  is 
exhaled  from  the  minute  ends  of  arteries  ; and  that  these  ex- 
tremities first  open  into  a hollow  vesicle,  from  whence  the  depo- 
sited juice  of  several  branches  flows  out  through  one  common 
frifice. 


248 


Of  the  Abdomen. 


the  intestines  from  the  irritation  to  which  it 
would,  perhaps,  otherwise  be  continually  ex- 
posed from  the  aliment ; and  which,  when  in 
a certain  degree,  excites  a painful  disorder 
called  colic , a name  given  to  the  disease,  be- 
cause its  most  usual  seat  is  in  the  intestinum 
colon. 

The  intestines  are  likewise  frequently  dis- 
tended with  air,  and  this  distention  sometimes 
occasions  pain,  and  constitutes  the  flatulent 
colic. 

The  arteries  of  the  intestines  are  continu- 
ations of  the  mesenteric  arteries,  which  are 
derived  in  two  considerable  branches  from  the 
aorta. — The  redundant  blood  is  carried  back 
into  the  vena  portarum. 

In  the  rectum  the  veins  are  called  hemor- 
rhoidal^ and  are  there  distinguished  into  inter- 
nal and  external : the  first  are  branches  of  the 
inferior  mesenteric  vein,  but  the  latter  pass 
into  other  veins.  Sometimes  these  veins  are 
distended  with  blood  from  obstructions,  from 
weakness  of  their  coats,  or  from  other  causes, 
and  what  we  call  the  hemorrhoids  takes  place. 
In  this  disease  they  are  sometimes  ruptured ; 
and  the  discharge  of  blood  which  consequent- 
ly follows,  has  probably  occasioned  them  to  be 
called  hemorrhoidal  veins. 

The  nerves  of  the  intestines  are  derived 
from  the  eighth  pair. 

Sect.  VI.  Of  the  Mesentery. 

The  name  of  the  mesentery  implies  its  sim- 
ulation amidst  the  intestines.  It  is  in  fact  a 


Of  the  Abdomen. 


249 


part  of  the  peritonaeum,  being  a reduplica- 
tion * of  that  membrane  from  each  side  of  the 
lumbar  vertebrae,  to  which  it  is  firmly  attach- 
ed, so  that  it  is  formed  of  two  laminae,  con- 
nected to  each  other  by  cellular  membrane. 

The  intestines,  in  their  different  circumvo- 
lutions, form  a great  number  of  arches,  and 
the  mesentery  accompanies  them  through  all 
these  turns  ; but  by  being  attached  only  to  the 
hollow  part  of  each  arch,  it  is  found  to  have 
only  a third  of  the  extent  of  the  intestines. 

That  part  of  this  membrane  which  accom- 
panies the  small  intestines  is  the  mesentery , 
properly  so  called  ; but  those  parts  of  it  which 
are  attached  to  the  colon  and  rectum  are  dis- 
tinguished by  the  names  of  meso-colon  and  me- 
so-rectum. 

There  are  many  conglobate  glands  dispers- 
ed through  this  double  membrane,  through 
which  the  lacteals  and  lymphatics  pass  in  their 
way  to  the  thoracic  duct.  The  blood-vessels 
of  the  mesentery  were  described  in  speaking 
of  the  intestines. 

I i 


* He  who  only  reads  of  the  reduplication  of  membranes, 
will  perhaps  not  easily  understand  how  the  perimnaum  and 
pleura  are  reflected  over  the  viscera  in  their  several  cavities  ; 
for  one  of  these  serves  the  same  purposes  in  the  thorax  that 
the  other  does  in  the  abdomen.  This  disposition,  for  the  dis- 
covery of  which  we  are  indebted  to  modern  anatomists,  con- 
stitutes a curious  part  of  anatomical  knowledge  : but  the  stu- 
dent, unaided  by  experience,  and  assisted  only  by  what  the  li- 
mits of  this  work  would  permit  us  to  say  on  the  occasion,  would 
probably  imbibe  only  confused  ideas  of  the  matter  ; and  it  will 
perfectly  answer  the  present  purpose,  if  he  considers  the  me- 
sentery as  a membrane  attached  bv  one  of  its  sides  to  the  lum- 
bar vertebrae,  and  by  the  other  to  the  intestines. 


250 


Of  the  Abdomen . 


This  membrane,  by  its  attachment  to  the 
vertebrae,  serves  to  keep  the  intestines  in  their 
natural  situation.  The  idea  usually  formed  of 
the  colic  called  miserere , is  perfectly  errone- 
ous ; it  being  impossible  that  the  intestines 
can  be  twisted,  as  many  suppose  they  are,  in 
that  disease,  their  attachment  to  the  mesente- 
ry effectually  preventing  such  an  accident — 
but  a disarrangement  sometimes  takes  place 
in  the  intestinal  canal  itself,  which  is  produc- 
tive of  disagreeable  and  sometimes  fatal  con- 
sequences.— This  is  by  an  introsusception  of 
the  intestine,  an  idea  of  which  may  be  easily 
formed,  by  taking  the  finger  of  a glove,  and 
involving  one  part  of  it  within  the  other* 

If  inflammation  takes  place,  the  stricture  in 
this  case  is  increased,  and  the  peristaltic  mo- 
tion of  the  intestines  (by  which  is  meant  the 
progressive  motion  of  the  faeces  downwards) 
is  inverted,  and  what  is  called  the  iliac  passion 
takes  place.  The  same  effects  may  be  occa- 
sioned by  a descent  of  the  intestine,  or  of  the 
omentum  either  with  it  or  by  itself,  and  thus 
constituting  what  is  called  an  hernial  rupture  ; 
a term  by  which  in  general  is  meant  the  falling 
down  or  protrusion  of  any  part  of  the  intes- 
tine or  omentum,  which  ought  naturally  to  be 
contained  within  the  cavity  of  the  belly. 

To  convey  an  idea  of  the  manner  in  which 
such  a,  descent  takes  place,  it  will  be  necessa- 
ry to  observe,  that  the  lower  edge  of  the  ten- 
don of  the  musculus  obliquus  externus,  is 
stretched  from  the  fore-part  of  the  os  ilium 
or  haunch-bone  of  the  os  pubis,  and  consti- 
tutes what  is  called  PouparVs  or  Fallopius's  li - 


Of  the  Abdomen. 


251 


garment,  forming  an  opening,  through  which 
pass  the  great  crural  artery  and  vein.  Near 
the  os  pubis  the  same  tendinous  fibres  are  se- 
parated from  each  other,  and  form  an  opening 
on  each  side,  called  the  abdominal  ring , through 
which  the  spermatic  vessels  pass  in  men,  and 
the  ligamenta  uteri  in  women.  In  consequence 
of  violent  efforts,  or  perhaps  of  natural  causes, 
the  intestines  are  found  sometimes  to  pass 
through  these  openings  ; but  the  peritonaeum 
which  incloses  them  when  in  their  natural  ca- 
vity, still  continues  to  surround  them  even  in 
their  descent.  This  membrane  does  not  be- 
come torn  or  lacerated  by  the  violence,  as 
might  be  easily  imagined ; but  its  dilatibility 
enables  it  to  pass  out  with  the  viscus,  which 
it  incloses  as  it  were  in  a bag,  and  thus  forms 
what  is  called  the  hernial  sac. 

If  the  hernia  be  under  Poupart’s  ligament, 
it  is  called  femoral  ; if  in  the  groin,  inguinal ;* 
and  scrotal , if  in  the  scrotum-  Different  names 
are  likewise  given  to  the  hernia  as  the  con- 
tents of  the  sac  differ,  whether  of  omentum 
only  or  intestine,  or  both: — but  these  defini- 
tions more  properly  belong  to  the  province  of 
surgery. 

Sect.  VIL  Of  the  Pancreas . 

The  pancreas  is  a conglomerate  gland 
placed  behind  the  bottom  of  the  stomach, 
towards  the  first  vertebra  of  the  loins  ; shaped 

* The  hernia  congenita  will  be  considered  with  the  male  or- 
gans of  generation,  with  which  it  is  intimately  connected. 


252 


Of  the  Abdomen. 


like  a dog’s  tongue,  with  its  point  stretched 
out  towards  the  spleen,  and  its  other  end  ex- 
tending towards  the  duodenum.  It  is  about 
eight  fingers  breadth  in  length,  two  or  three 
in  width,  and  one  in  thickness. 

This  viscus,  which  is  of  a yellowish  colour, 
somewhat  inclined  to  red,  is  covered  with  a 
membrane  which  it  derives  from  the  peritonae- 
um. Its  arteries,  which  are  rather  numerous 
than  large,  are  derived  chiefly  from  the  sple- 
nic and  hepatic,  and  its  veins  pass  into  the 
veins  of  the  same  name. — Its  nerves  are  de- 
rived from  the  intercostal. 

The  many  little  glands  of  which  it  has  been 
observed  the  pancreas  is  composed,  all  serve 
to  secrete  a liquor  called  the  pancreatic  juice , 
which  in  its  colour,  consistence,  and  other  pro- 
perties, does  not  seem  to  differ  from  the  sali- 
va. Each  of  these  glands  sends  out  a little 
excretory  duct,  which,  uniting  with  others, 
help  to  form  larger  ducts ; and  all  these  at  last 
terminate  in  one  common  excretory  duct  (first 
discovered  by  Virtsungus  in  1642),  which 
runs  through  the  middle  of  the  gland,  and  is 
now  usually  called  ductus  pancreaticus  Virt- 
sungi.  This  canal  opens  into  the  intestinum 
duodenum,  sometimes  by  the  same  orifice  with 
the  biliary  duct,  and  sometimes  by  a distinct 
opening.  The  liquor  it  discharges  being  of  a 
mild  and  insipid  nature,  serves  to  dilute  the 
alimentary  pulp,  and  to  incorporate  it  more 
easily  with  the  bile. 


Of  the  Abdomen. 


253 


Sect.  VIII.  Of  the  Liver. 

The  liver  is  a viscus  of  considerable  size, 
and  of  a reddish  colour ; convex  superiorly 
and  anteriorly  where  it  is  placed  under  the 
ribs  and  diaphragm,  and  of  an  unequal  sur- 
face posteriorly.  It  is  chiefly  situated  in  the 
right  hypochondrium,  and  under  the  false  ribs ; 
but  it  likewise  extends  into  the  epigastric  re- 
gion, where  it  borders  upon  the  stomach.  It 
is  covered  by  a production  of  the  peritonaeum, 
which  serves  to  attach  it  by  three  oi  its  redu- 
plications to  the  false  ribs.  These  reduplica- 
tions are  called  ligaments , though  very  differ- 
ent in  their  texture  from  what  are  called  by 
the  same  name  in  other  parts  of  the  body.  The 
umbilical  cord,  too,  which  in  the  foetus  is  per- 
vious, gradually  becomes  a simple  ligament 
after  birth  ; and,  by  passing  to  the  liver,  serves 
likewise  to  secure  it  in  its  situation. 

At  the  posterior  part  of  this  organ  where 
the  umbilical  vessels  enter,  it  is  found  divid- 
ed into  two  lobes.  Of  these,  the  largest  is 
placed  in  the  right  hypochondrium ; the  other, 
which  covers  part  of  the  stomach,  is  called 
the  little  lobe.  All  the  vessels  which  go  to  the 
liver  pass  in  at  the  fissure  we  have  mention- 
ed ; and  the  production  of  the  peritonaeum, 
which  invests  the  liver,  was  described  by  Glis- 
son,  an  English  anatomist,  as  accompanying 
them  in  their  passage,  and  surrounding  them 
like  a glove  ; hence  this  production  has  been 
commonly  known  by  the  name  of  capsula  of 
Glisson  : but  it  appears  to  be  chiefly  a continu- 


254 


Of  the  Abdomen. 


ation  of  the  cellular  membrane  which  covers 
the  vena  portse  ventralis. 

The  liver  was  considered  by  the  ancients  as 
an  organ  destined  to  prepare  and  perfect  the 
blood ; but  later  discoveries  have  proved,  that 
this  opinion  was  wrong,  and  that  the  liver  is  a 
glandular  substance  formed  for  the  secretion 
of  the  bile. 

The  blood  is  conveyed  to  the  liver  by  the 
hepatic  artery  and  the  vena  portse.  This  is 
contrary  to  the  mode  of  circulation  in  other 
parts,  where  veins  only  serve  to  carry  off  the 
redundant  blood  : but  in  this  viscus  the  hepa- 
tic artery,  which  is  derived  from  the  cseliac,  is 
principally  destined  for  its  nourishment ; and 
the  vena  portse,  which  is  formed  by  the  union 
of  the  veins  from  most  of  the  abdominal  vis- 
cera, furnishes  the  blood  from  which  the  bile 
is  chiefly  to  be  separated  ; so  that  these  two 
series  of  vessels  serve  very  distinct  purposes. 
The  vena  portae,  as  it  is  ramified  through  the 
liver,  performs  the  office  both  of  a vein  and 
an  artery  ; for  like  the  former  it  returns  the 
blood  from  the  extremities  of  arteries,  while 
as  the  latter  it  prepares  it  for  secretion. 

The  nerves  of  the  liver  are  branches  of  the 
intercostal  and  par  vagum.  The  bile,  after  be- 
ing separated  from  the  mass  of  blood,  in  a 
manner  of  which  mention  will  be  made  in 
another  place,  is  conveyed  out  of  this  organ 
by  very  minute  excretory  ducts,  called  poribi- 
liarii ; these  uniting  together  like  the  excreto- 
ry ducts  in  the  pancreas,  gradually  form  larger 
ones,  which  at  length  terminate  in  a considera- 
ble canal  called  ductus  hepaticus. 


Of  the  Abdomen. 


255 


Sect.  IX.  Of  the  Gall-bladder. 

The  gall-bladder  is  a little  membranous 
bag,  shaped  like  a pear,  and  attached  to  the 
posterior  and  almost  inferior  part  of  the  great 
lobe  of  the  liver. 

It  has  two  tunics  ; of  which  the  exterior 
one  is  a production  of  the  peritonaeum.  The 
interior,  or  villous  coat,  is  supplied  with  a mu- 
cus that  defends  it  from  the  acrimony  of  the 
bile.  These  two  coverings  are  intimately  con- 
nected by  means  of  cellular  membrane,  which 
from  its  firm  glistening  appearance  has  gene- 
rally been  spoken  of  as  a muscular  tunic. 

The  gall-bladder  is  supplied  with  blood- 
vessels from  the  hepatic  arteries.  These 
branches  are  called  the  cystic  arteries , and. 
the  cystic  veins  carry  back  the  blood. 

Its  nerves  are  derived  from  the  same  origin 
as  those  of  the  liver. 

The  neck  of  the  gall-bladder  is  continued 
in  the  form  of  a canal  called  ductus  cysticus, 
which  soon  unites  with  the  ductus  hepaticus 
we  described  as  the  excretory  duct  of  the  li- 
ver ; and  forming  one  common  canal,  takes  the 
name  of  ductus  coledochus  communis , through 
which  both  the  cystic  and  hepatic  bile  are  dis- 
charged into  the  duodenum.  This  canal  opens 
into  the  intestine  in  an  oblique  direction,  first 
passing  through  the  exterior  tunic,  and  then 
piercing  the  other  coats  after  running  between 
each  of  them  a very  little  way.  This  cecono- 
my  serves  two  useful  purposes ; — to  promote 
the  discharge  of  bile  and  to  prevent  its  return. 


256 


Of  the  Abdomen. 


The  bile  may  be  defined  to  be  a natural  li- 
quid soap,  somewhat  unctuous  and  bitter,  and 
of  a yellowish  colour,  which  easily  mixes  with 
water,  oil,  and  vinous  spirits,  and  is  capable 
of  dissolving  resinous  substances.  From  some 
late  experiments  made  by  M.  Cadet,*  it  ap- 
pears to  be  formed  of  an  animal  oil,  combined 
with  the  alkaline  base  of  sea-salt,  a salt  of  the 
nature  of  milk,  and  a calcareous  earth  which 
is  slightly  ferruginous. 

Its  definition  seems  sufficiently  to  point  out 
the  uses  for  which  it  is  intended.f  It  blends 
the  alimentary  mass,  by  dividing  and  attenu- 
ating it ; corrects  the  too  great  disposition  to 
acescency,  which  the  aliment  acquires  in  the 
stomach ; and  finally,  by  its  acrimony,  tends 
to  excite  the  peristaltic  motion  of  the  intes- 
tines. 

After  what  has  been  said,  it  will  be  conceiv- 
ed that  there  are  two  sorts  of  bile ; one  of 
which  is  derived  immediately  from  the  liver 
through  the  hepatic  duct,  and  the  other  from 
the  gall-bladder.  These  two  biles,  however, 
do  not  essentially  differ  from  each  other.  The 
hepatic  bile  indeed  is  milder,  and  more  liquid 
than  the  cystic,  which  is  constantly  thicker 
and  yellower;  and  by  being  bitterer,  seems  to 
possess  greater  activity  than  the  other. 

Every  body  knows  the  source  of  the  hepatic 
, bile,  that  it  is  secreted  from  the  mass  of  blood 
by  the  liver ; but  the  origin  of  the  cystic  bile 

* Mem.  de  1’  Acad,  des  Sciences,  1767. 

f The  ancients,  who  were  not  acquainted  with  the  real  use 
of  the  liver,  considered  the  bile  as  an  excrementitious  and  use- 
less fluid. 


Of  the  Abdomen.  257 

has  occasioned  no  little  controversy  amongst 
anatomical  writers.  There  are  some  who  con- 
tend, that  it  is  separated  in  the  substance  of 
the  liver,  from  whence  it  passes  into  the  gall- 
bladder through  particular  vessels.  In  deer, 
and  in  some  other  quadrupeds,  as  well  as  in 
several  birds  and  fishes,  there  is  an  evident 
communication,  by  means  of  particular  ves- 
sels, between  the  liver  and  the  gall-bladder. 
Bianchi,  Winslow,  and  others,  have  asserted 
the  existence  of  such  vessels  in  the  human 
subject,  and  named  them  hepaticystic  ducts; 
but  it  is  certain  that  no  such  ducts  exist. — In 
obstructions  of  the  cystic  duct,  the  gall-blad- 
der has  been  found  shrivelled  and  empty:  so 
that  we  may  consider  the  gall-bladder  as  a reser- 
voir of  hepatic  bile  ; and  that  it  is  an  establish- 
ed fact  that  the  whole  of  the  bile  contained  in 
the  gall-bladder  is  derived  from  the  liver ; that 
it  passes  from  the  hepatic  to  the  cystic  duct, 
and  from  that  to  the  gall-bladder.  The  differ- 
ence in  the  colour,  consistence,  and  taste  of 
the  bile,  is  merely  the  consequence  of  stagna- 
tion and  absorption.  When  the  stomach  is 
distended  with  aliment,  this  reservoir  under- 
goes a certain  degree  of  compression,  and  the 
bile  passes  out  into  the  intestinal  canal  ; and 
in  the  efforts  to  vomit,  the  gall-bladder  seems 
to  be  constantly  affected,  and  at  such  times  dis- 
charges itself  of  its  contents. 

Sometimes  the  bile  concretes  in  the  gall- 
bladder, so  as  to  form  what  are  called  gall - 

K k 


258 


Of  the  Abdomen. 


stones .*  When  these  concretions  pass  into 
the  cystic  duct,  they  sometimes  occasion  ex- 
quisite pain,  by  distending  the  canal  in  their 
way  to  the  duodenum ; and  by  lodging  in  the 
ductus  choledochus  communis,  and  obstruct- 
ing the  course  of  the  bile,  this  fluid  will  be 
absorbed,  and  by  being  carried  back  into  the 
circulation  occasion  a temporary  jaundice. 

Sect.  X.  Of  the  Spleen. 

The  spleen  is  a soft  and  spongy  viscus,  of 
a bluish  colour,  and  about  five  or  six  fingers 
breadth  in  length,  and  three  in  width,  situated 
in  the  left  hypochondrium,  between  the  sto- 
mach and  the  false  ribs.  That  side  of  it  which 
is  placed  on  the  side  of  the  ribs  is  convex  ; and 
the  other,  which  is  turned  toward  the  stomach, 
is  concave. 

The  splenic  artery,  which  is  a branch  from 
the  cteliac,  supplies  this  viscus  with  blood,  and 
a vein  of  the  same  name  carries  it  back  into 
the  vena  portae. 

Its  nerves  are  derived  from  a particular 
plexus  called  the  splenic , which  is  formed  by 
branches  of  the  intercostal  nerve,  and  by  the 
eighth  pair,  or  par  vagum. 

The  ancients,  who  supposed  two  sorts  of 
bile,  considered  the  spleen  as  the  receptacle 
of  what  they  called  atra  bills.  Havers,  who 

* These  concretions  sometimes  remain  in  the  gall-bladder 
without  causing  any  uneasiness.  Dr.  Heberden  relates,  that  a 
gall-stone  weighing  two  drams  was  found  in  the  gall-bladder  of 
the  late  Lord  Bath,  though  he  had  never  complained  of  the 
jaundice,  nor  of  any  disorder  which  he  could  attribute  to  that 
cause.  Med.  'Trans.  Vol.  ii. 


Of  the  Abdomen . 


259 


wrote  professedly  on  the  bones,  determined  its 
use  to  be  that  of  secreting  the  synovia  ; and 
the  late  Mr.  Hewson  imagined,  that  it  concur- 
red with  the  thymus  and  lymphatic  glands  of 
the  body  in  forming  the  red  globules  of  -the 
blood.  All  these  opinions  seem  to  be  equally 
fanciful.  The  want  of  an  excretory  duct  has 
occasioned  the  real  use  of  this  viscus  to  be 
still  doubtful.  Perhaps  the  blood  undergoes 
some  change  in  it,  which  may  assist  in  the  pre- 
paration of  the  bile.  This  is  the  opinion  of 
the  generality  of  modern  physiologists  ; and 
the  great  quantity  of  blood  with  which  it  is 
supplied,  together  with  the  course  of  its  veins 
into  the  vena  portte,  seem  to  render  this  no- 
tion probable. 

Sect.  XI.  Of  the  Glandule  Renales,  Kidneys, 
and  Ureters. 

The  glandulte  renales,  which  were  by  the 
ancients  supposed  to  secrete  the  atra  bilis,  and 
by  them  named  capsules  atrabilares , are  two 
flat  bodies  of  an  irregular  figure,  one  on  each 
side  between  the  kidney  and  the  aorta. 

In  the  foetus  they  are  as  large  as  the  kidneys  : 
but  they  do  not  increase  afterwards  in  propor- 
tion to  those  parts  ; and  in  adults  and  old  peo- 
ple they  are  generally  found  shrivelled,  and 
much  wasted.  They  have  their  arteries  and 
veins.  Their  arteries  usually  arise  from  the 
splenic  or  the  emulgent,  and  sometimes  from 
the  aorta  ; and  their  veins  go  to  the  neighbour- 
ing veins,  or  to  the  vena  cava.  Their  nerves 
are  branches  of  the  intercostal. 


260  Of  the  Abdomen. 

The  use  of  these  parts  is  not  yet  perfectly 
known.  In  the  foetus  the  secretion  of  urine 
must  be  in  a very  small  quantity,  and  a part 
of  the  blood  may  perhaps  then  pass  through 
these  channels,  which  in  the  adult  is  carried  to 
the  kidneys  to  supply  the  matter  of  urine. 

The  kidneys  are  two  in  number,  situated 
one  on  the  right  and  the  other  on  the  left  side 
in  the  lumbar  region,  between  the  last  false 
rib  and  the  os  ilium,  by  the  sides  of  the  verte- 
brae. Each  kidney  in  its  figure  resembles  a 
sort  of  bean,  which  from  its  shape  is  called 
hidney-bean.  The  concave  part  of  each  kidney 
is  turned  towards  the  aorta  and  vena  cava  as- 
cendens.  They  are  surrounded  by  a good 
deal  of  fat,  and  receive  a coat  from  the  peri- 
tonaeum ; and  when  this  is  removed,  a very 
fine  membrane  is  found  investing  their  sub- 
stance and  the  vessels  which  ramify  through 
them. 

Each  kidney  has  a considerable  artery  and 
vein,  which  are  called  the  emulgent.  The  ar- 
tery is  a branch  from  the  aorta,  and  the  vein 
passes  into  the  vena  cava.  Their  nerves, 
which  every  where  accompany  the  blood- 
vessels, arise  from  a considerable  plexus, 
which  is  derived  from  the  intercostal. 

In  each  kidney,  which  in  the  adult  is  of  a 
pretty  firm  texture,  there  are  three  substances 
to  be  distinguished.*  The  outer  part  is  glan- 
dular or  cortical,  beyond  this  is  the  vascular 

* The  kidneys  in  the  fcetus  are  distinctly  lobulated  ; but  in 
the  adult  they  become  perfectly  firm,  smooth,  and  regular. 


Of  the  Abdome?i. 


261 


or  tubular  substance,  and  the  inner  part  is  pa- 
pillary or  membranous. 

It  is  in  the  cortical  part  of  the  kidney  that 
the  secretion  is  carried  on ; the  urine  being 
here  received  from  the  minute  extremities  of 
the  capillary  arteries,  is  conveyed  out  of  this 
cortical  substance  by  an  infinite  number  of  ve- 
ry small  cylindrical  canals  or  excretory  ves- 
sels, which  constitute  the  tubular  part.  These 
tubes,  as  they  approach  the  inner  substance 
of  the  kidney  gradually  unite  together ; and 
thus  forming  larger  canals,  at  length  termi- 
nate in  ten  or  twelve  little  protuberances  call- 
ed papilla,  the  orifices  of  which  may  be  seen 
without  the  assistance  of  glasses.  These  pa- 
pillae open  into  a small  cavity  or  reservoir 
called  the  pelvis  of  the  kidney , and  formed  by 
a distinct  membranous  bag  which  embraces 
the  papillae.  From  this  pelvis  the  urine  is 
conveyed  through  a membranous  canal  which 
passes  out  from  the  hollow  side  of  the  kidney, 
a little  below  the  blood-vessels,  and  is  called 
ureter. 

The  ureters  are  each  about  as  large  as  a 
common  writing-pen.  They  are  somewhat 
curved  in  their  course  from  the  kidneys,  like 
the  letter  f and  at  length  terminate  in  the  pos- 
terior and  almost  inferior  part  of  the  bladder, 
at  some  distance  from  each  other.  They  pass 
into  the  bladder  in  the  same  manner  as  the 
ductus  choledochus  communis  passes  into  the 
intestinum  duodenum,  not  by  a direct  passage, 
but  by  an  oblique  course  between  the  two 
coats ; so  that  the  discharge  of  urine  into  the 
bladder  is  promoted,  whilst  its  return  is  pre- 


262 


Of  the  Abdomen . 


vented.  Nor  does  this  mode  of  structure  pre- 
vent the  passage  of  fluids  only  from  the  blad- 
der into  the  ureters,  but  likewise  air : — for  air 
thrown  into  the  bladder  inflates  it,  and  it  con- 
tinues to  be  distended  if  a ligature  is  passed 
round  its  neck  ; which  seems  to  prove  suffici- 
ently that  it  cannot  pass  into  the  ureters. 

Sect.  XII.  Of  the  Urinary  Bladder. 

The  urinary  bladder  is  a membranous  and 
muscular  bag  of  an  oblong  roundish  shape, 
situated  in  the  pelvis,  between  the  os  pubis 
and  intestinum  rectum  in  men,  and  between 
the  os  pubis  and  uterus  in  women.  Its  up- 
per and  widest  part  is  usually  called  the  bot- 
tom, its  narrow  part  the  neck  of  the  bladder ; 
the  former  only  is  covered  by  the  peritonaeum. 

The  bladder  is  formed  of  three  coats,  con- 
nected together  by  means  of  cellular  mem- 
brane. The  external  or  peritonaeal,  is  only  a 
partial  one,  covering  the  upper  and  back  part 
of  the  bladder.  The  middle,  or  muscular 
coat,  is  composed  of  irritable,  and  of  course 
muscular  fibres,  which  are  most  collected 
around  the  neck  of  the  bladder,  but  not  so 
as  to  form  a distinct  muscle,  or  sphincter,  as 
the  generality  of  anatomists  have  hitherto  sup- 
posed. 

The  inner  coat,  though  much  smoother,  has 
been  said  to  resemble  the  villous  tunic  of  the 
intestines,  and  like  that  is  provided  with  a 
mucus,  which  defends  it  against  the  acrimony 
of  the  urine. 


263 


Of  the  Abdomen. 

It  will  be  easily  conceived  from  what  has 
been  said,  that  the  kidneys  are  two  glandular 
bodies,  through  which  a saline  and  excremen- 
titious  fluid  called  urine  is  constantly  filtering 
from  the  mass  of  blood. 

While  only  a small  quantity  of  urine  is  col- 
lected in  the  bladder,  it  excites  no  kind  of  un- 
easiness ; but  when  a greater  quantity  is  ac- 
cumulated, so  that  the  bladder  is  distended  in 
a certain  degree,  it  excites  in  us  a certain  sen- 
sation, which  brings  on  as  it  were  a voluntary 
contraction  of  the  bladder  to  promote  its  dis- 
charge.— But  this  contraction  is  not  effected 
by  the  muscular  fibres  of  the  bladder  alone : 
for  all  the  abdominal  muscles  contract  in  obe- 
dience to  our  will,  and  press  downwards  all 
the  viscera  of  the  lower  belly  ; and  these  pow- 
ers being  united,  at  length  overcome  the  re- 
sistance of  the  fibres  surrounding  the  neck  of 
the  bladder,  which  dilates  and  affords  a pas- 
sage to  the  urine  through  the  urethra. 

The  frecpiency  of  this  evacuation  depends 
on  the  quantity  of  urine  secreted  ; on  the  de- 
gree of  acrimony  it  possesses  ; on  the  size  of 
the  bladder,  and  on  its  degree  of  sensibility. 

The  urine  varies  much  in  its  colour  and 
contents.  These  varieties  depend,  on  age,  sex, 
climate,  diet,  and  other  circumstances.  In  in- 
fants it  is  generally  a clear  watery  fluid,  with- 
out smell  or  taste.  As  we  advance  in  life,  it 
acquires  more  colour  and  smell,  and  becomes 
more  impregnated  with  salts.  In  old  people 
it  becomes  still  more  acrid  and  fetid. 

In  a healthy  state  it  is  nearly  of  a straw  co- 
lour.— After  being  kept  for  some  time,  it  de- 


264 


Of  the  Abdomen. 


posites  a tartarous  matter,  which  is  found 
to  be  composed  chiefly  of  earth  and  salt,  and 
soon  incrusts  the  sides  of  the  vessel  in  which 
it  is  contained.  While  this  separation  is  tak- 
ing place,  appearances  like  minute  fibres  or 
threads  of  a whitish  colour  may  be  seen  in  the 
middle  of  the  urine,  and  an  oily  scum  observ- 
ed floating  on  its  surface.  So  that  the  most 
common  appearances  of  the  urine  are  suffici- 
ent to  ascertain  that  it  is  a watery  substance, 
impregnated  with  earthy,  saline,  and  oily  par- 
ticles. 

The  urine  is  not  always  voided  of  the  same 
colour  and  consistence:  for  these  are  found  to 
depend  on  the  proportion  of  its  watery  part  to 
that  of  its  other  constituent  principles. — Its  co- 
lour and  degree  of  fluidity  seem  to  depend  on 
the  quantity  of  saline  and  inflammable  parti- 
cles contained  in  it : so  that  an  increased  pro- 
portion of  those  parts  will  constantly  give  the 
urine  a higher  colour,  and  add  to  the  quanti- 
ty of  sediment. 

The  variety  in  the  appearance  of  the  urine, 
depends  on  the  nature  and  quantity  of  solid 
and  fluid  aliment  we  take  in ; and  it  is  like- 
wise occasioned  by  the  different  state  of  the 
urinary  vessels,  by  which  we  mean  the  chan- 
nels through  which  it  is  separated  from  the 
blood,  and  conveyed  through  the  pelvis  into 
the  ureters.  The  causes  of  calculous  concre- 
tions in  the  urinary  passages,  are  to  be  looked 
for  in  the  natural  constitution  of  the  body, 
mode  of  life,  &c. 

It  having  been  observed,  that  after  drink- 
ing any  light  wine  or  Spa  water,  it  very  soon 


Of  the  Abdomen.  26  5 

passed  off  by  urine,  it  has  been  supposed  by 
some,  that  the  urine  is  not  altogether  convey- 
ed to  the  bladder  by  the  ordinary  course  of 
circulation,  but  that  there  must  certainly  exist 
some  other  shorter  means  of  communication, 
perhaps  by  certain  vessels  between  the  sto- 
mach and  the  bladder,  or  by  a retrograde  motion 
in  the  lymphatics.  But  it  is  certain,  that  if  we 
open  the  belly  of  a dog,  press  out  the  urine 
from  the  bladder,  pass  a ligature  round  the 
emulgent  arteries,  and  then  sew  up  the  abdo- 
men, and  give  him  even  the  most  diuretic  li- 
quor to  drink,  the  stomach  and  other  chan- 
nels will  be  distended  with  it,  but  not  a drop 
of  urine  will  be  found  to  have  passed  into  the 
bladder ; or  the  same  thing  happens  when  a 
ligature  is  thrown  round  the  two  ureters.  This 
experiment  then  seems  to  be  a sufficient  proof, 
that  all  the  urine  we  evacuate,  is  conveyed  to 
the  kidneys  through  the  emulgent  arteries,  in 
the  manner  we  have  described. — It  is  true,  that 
wine  and  other  liquors  promote  a speedy  eva- 
cuation of  urine : but  the  discharge  seems  to 
be  merely  the  effect  of  the  stimulus  they  occa- 
sion \ by  which  the  bladder  and  urinary  parts 
are  solicited  to  a more  copious  discharge  of  the 
urine,  which  was  before  in  the  body,  and  not 
immediately  of  that  which  was  last  drank  ; and 
this  increased  discharge,  if  the  supply  is  kept 
up,  will  continue  : nor  will  this  appear  won- 
derful, if  we  consider  the  great  capacity  of  the 
vessels  that  go  to  the  kidneys  ; the  constant  sup- 
ply of  fresh  blood  that  is  essential  to  health  ; 
and  the  rapidity  with  which  it  is  incessantly 

LI 


266  Of  the  Abdomen. 

circulated  through  the  heart  to  all  parts  of  the 
body. 

Sect.  XIII.  Of  Digestion. 

We  are  now  proceeding  to  speak  of  diges- 
tion, which  seems  to  be  introduced  in  this 
place  with  propriety,  after  a description  of  the 
abdominal  viscera,  the  greater  part  of  which 
contribute  to  this  function.  By  digestion  is  to 
be  understood,  the  changes  the  aliment  under- 
goes for  the  formation  of  chyle  : — these  chan- 
ges are  effected  in  the  mouth,  stomach,  and 
small  intestines. 

The  mouth,  of  which  every  body  has  a ge- 
neral knowledge,  is  the  cavity  between  the 
two  jaws,  formed  anteriorly  and  laterally  by 
the  lips,  teeth,  and  cheeks,  and  terminating 
posteriorly  in  the  throat. 

The  lips  and  cheeks  are  made  up  of  fat  and 
muscles,  covered  by  the  cuticle,  which  is  con- 
tinued over  the  whole  inner  surface  of  the 
mouth,  like  a fine  and  delicate  membrane. — 
Besides  this  membrane,  the  inside  of  the  mouth 
is  furnished  with  a spongy  and  very  vascular 
substance  called  therms,  by  means  of  which 
the  teeth  are  secured  in  their  sockets.  A simi- 
lar substance  covers  the  roof  of  the  mouth, 
and  forms  what  is  called  the  velum  pendulum 
palati , which  is  fixed  to  the  extremity  of  the 
arch  formed  by  the  ossa  maxillaria  and  ossa  pa- 
lati, and  terminates  in  a soft,  small,  and  coni- 
cal body,  named  uvula ; which  appears,  as  it 
were,  suspended  from  the  middle  of  the  arch 
over  the  basis  of  the  tongue. 


267 


Of  the  Abdomen * 

The  velum  pendulum  palati  performs  the 
office  of  a valve  between  the  cavity  of  the 
mouth  and  the  pharynx,  being  moved  by  se- 
veral muscles.* 

The  tongue  is  composed  of  several  mus- 
clesf  which  enable  it  to  perform  a variety  of 
motions  for  the  articulation  of  the  voice  ; for 
the  purposes  of  mastication  ; and  for  convey- 
ing the  aliment  into  the  pharynx.  Its  upper 
part  is  covered  with  papillse,  which  constitute 
the  organ  of  taste,  and  are  easily  to  be  dis- 
tinguished; it  is  covered  by  the  same  lpem- 
brane  that  lines  the  inside  of  the  mouth,  and 
which  makes  at  its  inferior  part  towards  its  ba- 
sis a reduplication  called  franum. 

Posteriorly,  under  the  velum  palati,  and  at 
the  basis  of  the  tongue,  is  the  pharynx  : which 
is  the  beginning  of  the  oesophagus,  stretched 
out  every  way,  so  as  to  resemble  the  top  of  a 
funnel,  through  which  the  aliment  passes  into 
the  stomach. 

The  mouth  has  a communication  with  the 
nostrils  at  its  posterior  and  upper  part : with 
the  ears,  by  the  Eustachian  tubes  ; with  the 
lungs,  by  means  of  the  larynx  ; . and  with  the 
stomach,  by  means  of  the  oesophagus. 

The  pharynx  is  constantly  moistened  by  a 
fluid,  secreted  by  two  considerable  glands  call- 
ed the  tonsils , one  on  each  side  of  the  velum 
palati.  These  glands,  from  their  supposed  re- 

* These  are  the  circumflexus  palati,  levator  palati  mollis,  pa- 
lato-pharyngasus,  constrictor  isthmi  faucium  and  azygos  uvulse. 
See  pages  191,  192,  193. 

f These  are,  the  genio-glossus,  hyo-glossus,  lingualis,  and 
stylo-glossus.  Seepage  191. 


268  Of  the  Abdomen. 

semblance  to  almonds,  have  likewise  been  call- 
ed cimygdalus. 

The  mouth  is  moistened  by  a considerable 
quantity  of  saliva.  This  fluid  is  derived  from 
the  parotid  glands  ; a name  which  by  its  ety- 
mology points  out  their  situation  to  be  neat  the 
ears.  They  are  two  in  number,  one  on  each 
side  under  the  os  malse  : and  they  are  of  the 
conglomerate  kind ; being  formed  of  many 
smaller  glands,  each  of  which  sends  out  a very 
small  excretory  duct,  which  unites  with  the 
rest,  to  form  one  common  channel,  that  runs 
over  the  cheek,  and  piercing  the  buccinator 
muscle,  opens  into  the  mouth  on  each  side,  by 
an  orifice  into  which  a bristle  may  be  easily  in- 
troduced.— Besides  these,  the  maxillary  glands, 
which  are  placed  near  the  inner  surface  of  the 
angle  of  the  lower  jaw  on  each  side  ; the  sub- 
lingual glands,  which  are  situated  at  the  root 
of  the  tongue  ; the  glands  of  the  palate,  which 
are  seated  in  the  velum  palati ; and  those  of 
the  cheeks,  lips,  &c.  together  with  many  other 
less  considerable  ones, — pour  the  saliva  into 
the  mouth  through  their  several  excretory 
ducts. 

The  saliva,  like  all  the  other  humors  of  the 
body,  is  found  to  be  different  in  different  peo- 
ple : but  in  general,  it  is  a limpid  and  insipid 
fluid,  without  smell  in  healthy  subjects ; and 
these  properties  would  seem  to  prove  that  it 
contains  very  few  saline  or  inflammable  parti- 
cles. 

The  uses  of  the  saliva  seem  to  be  to  moisten 
and  lubricate  the  mouth,  and  to  assist  in  re- 


269 


Of  the  Abdomen. 

ducing  the  aliment  into  a soft  pulp  before  it  is 
conveyed  into  the  stomach. 

The  variety  of  functions  which  are  constant- 
ly performed  by  the  living  body,  must  neces- 
sarily occasion  a continual  waste  and  dissipa- 
tion of  its  several  parts.  A great  quantity  is 
every  day  thrown  off  by  the  insensible  perspi- 
ration and  other  discharges  ; and  were  not  these 
losses  constantly  recruited  by  a fresh  supply  of 
chyle,  the  body  would  soon  effect  its  own  dis- 
solution. But  nature  has  very  wisely  favour- 
ed us  with  organs  fitted  to  produce  such  a sup- 
ply ; and  has  at  the  same  time  endued  us  with 
the  sensations  of  hunger  and  thirst,  that  our 
attention  may  not  be  diverted  from  the  neces- 
sary business  of  nutrition-  The  sensation  of 
hunger  is  universally  known ; but  it  would 
perhaps  be  difficult  to  describe  it  perfectly  in 
words.  It  may,  however,  be  defined  to  be  a 
certain  uneasy  sensation  in  the  stomach,  which 
induces  us  to  wish  for  solid  food ; and  which 
likewise  serves  to  point  out  the  proper  quan- 
tity, and  time  for  taking  it.  In  describing  the 
stomach,  mention  was  made  of  the  gastric  juice, 
as  every  where  lubricating  its  inner  coat.  This 
humor  mixes  itself  with  the  aliment  in  the  sto- 
mach, and  helps  to  prepare  it  for  its  passage 
into  the  intestines  ; but  when  the  stomach  is* 
perfectly  empty,  this  same  fluid  irritates  the. 
coats  of  the  stomach  itself,  and  produces  the 
sensation  of  hunger. 

A certain  proportion  of  liquid  aliment  is  re- 
quired to  assist  in  the  process  of  digestion,  and 
to  afford  that  moisture  to  the  body,  of  which 
there  is  such  a constant  dissipation. — Thirst 
induces  us  to  take  this  necessary  supply  of 


270 


Of  the  Abdomen. 


drink  ; and  the  seat  of  this  sensation  is  in  the 
tongue,  fauces,  and  oesophagus,  which  from 
their  great  sensibility  are  required  to  be  kept 
moist : for  though  the  fauces  are  naturally 
moistened  by  the  mucus  and  salival  juices  ; 
yet  the  blood,  when  deprived  of  its  watery 
part  or  rendered  acrimonious  by  any  natural 
causes,  never  fails  particularly  to  affect  these 
parts,  and  the  whole  alimentary  canal,  and  to 
occasion  thirst. — This  is  the  common  effect 
of  fevers  and  of  hard  labour,  by  both  which  too 
much  of  the  watery  part  of  the  blood  is  dis- 
sipated, 

It  has  been  observed,  that  the  aliment  un- 
dergoes some  preparation  in  the  mouth  before 
it  passes  into  the  stomach  ; and  this  prepara- 
tion is  the  effect  of  mastication.  In  treating  of 
the  upper  and  lower  jaws,  mention  was  made  of 
the  number  and  arrangement  of  the  teeth.  The 
upper  jaw  was  described  as  being  immoveable  ; 
but  the  lower  jaw  was  spoken  of  as  being  capable 
of  elevation  and  depression,  and  of  a grinding 
motion.  The  aliment,  when  first  carried  into 
the  mouth,  is  pressed  between  the  teeth  of  the 
two  jaws  by  a very  strong  and  frequent  motion 
of  the  lower  jaw;  and  the  tongue  and  the  cheeks 
assisting  in  this  process,  continue  to  replace  the 
food  between  the  teeth  till  it  is  perfectly  divid- 
ed, and  reduced  to  the  consistence  of  pulp. 
The  incisores  and  canini  divide  it  first  into 
smaller  pieces,  but  it  is  between  the  surfaces  of 
the  dentes  molares  by  the  grinding  motion  of 
the  jaw  that  the  mastication  is  completed. 

During  this  process  the  salival  glands  being 
gently  compressed  by  the  contraction  of  the 


271 


Of  the  Abdomen. 

muscles  that  move  the  lower  jaw,  pour  out  their 
saliva : this  helps  to  divide  and  break  down 
the  food,  which  at  length  becomes  a kind  of  pulp, 
and  is  then  carried  over  the  basis  of  the  tongue 
into  the  fauces.  But  to  effect  this  passage  into 
the  oesophagus,  it  is  necessary  that  the  other 
openings  which  were  mentioned  as  having  a 
communication  with  the  mouth  as  well  as  the 
pharynx,  should  be  closed;  that  none  of  the 
aliment,  whether  solid  or  liquid,  may  pass  into 
them,  whilst  the  pharynx  alone  is  dilated  to  re- 
ceive it : — And  such  a disposition  actually  takes 
place  in  a manner  we  will  endeavour  to  de- 
scribe. 

The  trachea  arteria,  or  windpipe,  through 
which  the  air  is  conveyed  to  the  lungs,  is  plac- 
ed before  the  oesophagus — in  the  act  of  swal- 
lowing ; therefore,  if  the  larynx  (for  so  the  up- 
per part  of  the  trachea  is  called)  is  not  closed, 
the  aliment  will  pass  into  it  in  its  way  to  the 
oesophagus.  But  this  is  prevented  by  a small 
and  very  elastic  cartilage,  called  epiglottis , which 
is  attached  only  to  the  fore-part  of  the  larynx  ; 
so  that  the  food  in  its  passage  to  the  oesopha- 
gus presses  down  this  cartilage,  which  then  co- 
vers the  glottis  or  opening  of  the  larynx  ; and 
at  the  same  time  the  velum  palati  being  capable 
of  some  degree  of  motion,  is  drawn  backwards 
by  its  muscles,  and  closes  the  openings  into  the 
nose  and  the  Eustachian  tubes. — This,  howe- 
ver, is  not  all.  The  larynx,  which  being  com- 
posed of  cartilaginous  rings,  cannot  fail  in  its 
ordinary  state  to  compress  the  membranous  ca- 
nal of  the  oesophagus,  is  in  the  act  of  degluti- 
tion carried  forwards  and  upwards  by  muscles 


.272 


Of  the  Abdomen. 

destined  for  that  purpose  ; and  consequently 
drawing  the  fore-part  of  the  pharynx  with  it, 
that  opening  is  fully  dilated.  When  the  ali- 
ment has  reached  the  pharynx,  its  descent  is 
promoted  by  its  own  proper  weight,  and  by  the 
muscular  fibres  of  the  cesophagus,  which  con- 
tinue to  contract  from  above  downwards,  until 
the  aliment  has  reached  the  stomach.  That 
these  fibres  have  no  inconsiderable  sharedn  de- 
glutition, any  person  may  experience,  by 
swallowing  with  his  head  downwards,  when  the 
descent  of  the  aliment  cannot  possibly  be  ef- 
fected by  its  weight. 

It  is  necessary  that  the  nostrils  and  the  lungs 
should  communicate  with  the  mouth,  for  the 
purposes  of  speech  and  respiration:  but  if  the 
most  minute  part  of  our  food  happens  to  be 
introduced  into  the  trachea,  it  never  fails  to 
produce  a violent  cough,  and  sometimes  the 
most  alarming  symptoms.  This  is  liable  to 
happen  when  we  laugh  or  speak  in  the  act  of 
deglutition  : the  food  is  then  said  to  have  passed 
the  wrong  way.  And  indeed  this  is  not  im- 
properly expressed : for  death  would  soon  fol- 
low, if  the  quantity  of  aliment  introduced  into 
the  trachea  should  be  sufficient  to  obstruct  the 
respiration  only  during  a very  short  time  ; or 
if  the  irritating  particles  of  food  should  not 
soon  be  thrown  up  again  by  means  of  the 
cough,  which  in  these  cases  very  seasonably 
increases  in  proportion  to  the  degree  of  irrita- 
tion. 

If  the  velum  palati  did  not  close  the  passage 
to  the  nostrils,  deglutition  would  be  performed 
with  difficulty,  and  perhaps  not  at  all ; for  the 


273 


Of  the  Abdomen. 

aliment  would  return  through  the  nose,  as  is 
sometimes  the  case  in  drinking.  Children, 
from  a deficiency  in  this  velum  palati,  have 
been  seen  to  die  a few  hours  after  birth ; and 
they  who  from  disease  or  any  other  causes 
have  not  this  part  perfect,  swallow  with  diffi- 
culty. 

The  aliment,  after  having  been  sufficiently 
divided  by  the  action  of  the  teeth,  and  attenu- 
ated by  the  saliva,  is  received  into  the  stomach, 
where  it  is  destined  to  undergo  a more  consi- 
derable change. 

The  properties  of  the  aliment  not  being  much 
altered  at  its  first  entrance  into  the  stomach, 
and  before  it  is  thoroughly  blended  with  the 
gastric  juice,  is  capable  of  irritating  the  inner 
coat  of  the  stomach  to  a certain  degree,  and 
occasions  a contraction  of  its  two  orifices. — In 
this  membranous  bag,  surrounded  by  the  abdo- 
minal viscera,  and  with  a certain  degree  of  na- 
tural heat,  the  aliment  undergoes  a constant 
agitation  by  means  of  the  abdominal  muscles 
and  of  the  diaphragm,  and  likewise  by  a cer- 
tain contraction  or  expansion  of  the  muscular 
fibres  of  the  stomach  itself.  By  this  motion, 
every  part  of  the  food  is  exposed  to  the  action 
of  the  gastric  juice,  which  gradually  divides 
and  attenuates  it,  and  prepares  it  for  its  pas- 
sage into  the  intestines. 

Some  observations  lately  published  by  Mr. 
Hunter  in  the  Philosophical  Transactions,  tend 
to  throw  considerable  light  on  the  principles  of 
digestion.  There  are  few  dead  bodies  in  which 
the  stomach,  at  its  great  end,  is  not  found  to 

M m 


274 


Of  the  Abdomen. 


be  in  some  degree  digested  Animals,  or 
parts  of  animals,  possessed  of  the  living  prin- 
ciple, when  taken  into  the  stomach,  are  not  in 
the  least  affected  by  the  action  of  that  viscus ; 
but  the  moment  they  lose  the  living  principle, 
they  become  subject  to  its  digestive  powers. 
This  seems  to  be  the  case  with  the  stomach, 
which  is  enabled  to  resist  the  action  of  its  juices 
in  the  living  body : but  when  deprived  of  the 
living  principle,  it  is  then  no  longer  able  to  resist 
the  powers  of  that  menstruum,  which  it  had  it- 
self formed  for  the  digestion  of  its  contents  ; 
the  process  of  digestion  appearing  to  be  conti- 
nued after  death.  This  is  confirmed  by  what 
happens  in  the  stomachs  of  fishes : they  fre- 
quently swallow,  without  mastication,  fish 
which  are  larger  than  the  digesting  parts  of  their 
stomach  can  contain  } and  in  such  cases,  that 
part  which  is  taken  into  the  stomach  is  more 

* The  Abbe  Spallanzani,  who  has  lately  written  upon  di- 
gestion, finds,  from  a variety  of  experiments,  made  upon  quadru- 
peds, birds,  and  fishes,  that  digestion  goes  on  for  some  time  after 
death,  though  far  less  considerable  than  in  living  animals  ; but 
heat  is  necessary  in  many  animals,  or  at  least  promotes  it  in  a 
much  greater  degree.  He  found  also,  that  when  the  stomach 
was  cut  out  of  the  body,  it  had  somewhat  of  the  power  of  diges- 
tion, though  this  was  trifling  when  compared  with  that  which 
took  place  when  the  stomach  was  left  in  the  body.  In  not  one 
of  the  animals  wa'  the  great  curvature  of  the  stomach  dissolved, 
or  much  eroded  after  death.  There  was  often  a little  erosion, 
especially  in  different  fishes  ; in  which,  when  he  had  cleared  the 
stomach  of  its  contents,  the  internal  coat’was  wanting.  In  other 
animals  there  was  only  a slight  excoriation  ; and  the  injury  in  all 
of  them  was  at  the  inferior  part,  or  great  curvature.  The  coats 
of  the  stomach  suffer  less  after  death  than  flesh,  or  part  of  the 
stomach  of  similar  animals  put  into  it : the  author  assigns  as  a 
reason  for  this,  that  these  bodies  are  invested  on  all  sides  by  the 
gastric  fluid,  whereas  it  only  acts  on  the  internal  surface  of  the 
stomach. 


Of  the  Abdomeiu 

or  less  dissolved,  while  that  part  which  re- 
mains in  the  oesophagus  is  perfectly  sound ; 
and  here,  as  well  as  in  the  human  body,  the 
digesting  part  of  the  stomach  is  often  reduced 
to  the  same  state  as  the  digested  part  of  the 
food.  These  appearances  tend  to  prove,  that 
digestion  is  not  effected  by  a mechanical  power, 
by  contractions  of  the  stomach,  or  by  heat ; 
but  by  a fluid  secreted  in  the  coats  of  the  sto- 
mach, which  is  poured  into  its  cavity,  and 
there  animalizes  the  food,  or  assimilates  it  to 
the  nature  of  blood. 

From  some  late  experiments  by  M.  Sage,  * 
it  appears,  that  inflammable  air  has  the  proper- 
ty of  destroying  and  dissolving  the  animal  tex- 
ture : and  as  we  swallow  with  the  substances 
which  serve  us  for  food  a great  quantity  of  at- 
mospherical air,  M.  Sage  thinks  it  possible, 
that  dephlogisticated,  which  is  its  principle, 
may  be  converted  in  the  stomach  into  inflam- 
mable air,  or  may  modify  into  inflammable  air 
a portion  of  the  oily  substance  which  is 
the  principle  of  aliments.  In  this  case,  would 
not  the  inflammable  air  (he  asks),  by  dissolv- 
ing our  food,  facilitate  its  conversion  into 
chyle  ? 

Be  this  as  it  may,  the  food  after  having  re- 
mained one,  two,  or  three  hours  in  the  stomach, 
is  converted  into  a greyish  pulp,  which  is  usu- 
ally called  chymus , a word  of  Greek  etymolo- 
gy, signifying  juice , and  some  few  milky  or 
chylous  particles  begin  to  appear. — But  the 

* Hist,  de  1’ A cademie  royals  des  Sciences,  Src.  pour  1784. 
mem.  15. 


276 


Of  the  Abdomen. 


term  of  its  residence  in  this  bag  is  proportion- 
ed to  the  nature  of  the  aliment,  and  to  the  state 
of  the  stomach  and  its  juices.  The  thinner  and 
more  perfectly  digested  parts  of  the  food  pass 
by  a little  at  a time  into  the  duodenum,  through 
the  pylorus,  the  fibres  of  which  relax  to  afford 
it  a passage  ; and  the  grosser  and  less  digested 
particles  remain  in  the  stomach,  till  they  ac- 
quire a sufficient  fluidity  to  pass  into  the  intes- 
tines, where  the  nature  of  the  chymus  is  per- 
fectly changed.  The  bile  and  pancreatic  juice 
which  flow  into  the  duodenum,  and  the  mucus, 
which  is  every  where  distilled  from  the  surface 
of  the  intestines,  mix  themselves  with  the  ali- 
mentary pulp,  which  they  still  farther  attenu- 
ate and  dissolve,  and  into  which  they  seem  to 
infuse  new  properties. 

Two  matters  very  different  from  each  other 
in  their  nature  and  destination,  are  the  result 
of  this  combination. — One  of  these,  which  is 
composed  of  the  liquid  parts  of  the  aliment, 
and  of  some  of  its  more  solid  particles,  ex- 
tremely divided  and  mixed  with  the  juices  we 
have  described,  constitutes  a very  mild,  sweet, 
and  whitish  fluid,  resembling  milk,  and  distin- 
guished by  the  name  of  chyle.  This  fluid  is  ab- 
sorbed by  the  lacteal  veins,  which  convey  it  in- 
to the  circulation,  where,  by  being  assimilated 
into  the  nature  of  blood,  it  affords  that  supply 
of  nutrition,  which  the  continual  waste  of  the 
body  is  found  to  require. — The  other  is  the  re- 
mains of  the  alimentary  mass  deprived  of  all 
its  nutritious  particles,  and  containing  only 
such  parts  as  were  rejected  by  the  absorbing 
mouths  of  the  lacteals.  This  grosser  part, 


Of  the  Abdomen.  277 

called  the  faces,  passes  on  through  the  course 
of  the  intestines,  to  be  voided  at  the  anus, 
as  will  be  explained  hereafter ; for  this  process 
in  the  (economy  cannot  be  well  understood  till 
the  motion  of  respiration  has  been  explained. 
But  the  structure  of  the  intestines  is  a subject 
which  may  be  properly  described  in  this  place, 
and  deserves  to  be  attended  to. 

It  has  been  already  observed,  that  the  intes- 
tinal canal  is  five  or  six  times  as  long  as  the  bo- 
dy, and  that  it  forms  many  circumvolutions  in 
the  cavity  of  the  abdomen,  which  it  traverses 
from  the  right  to  the  left,  and  again  from  the 
left  to  the  right ; in  one  place  descending,  and 
in  another  extending  itself  upwards.  It  was 
noticed  likewise,  that  the  inner  coat  of  the  in- 
testines, by  being  more  capacious  than  their  ex- 
terior tunics,  formed  a multitude  of  plates  plac- 
ed at  a certain  distance  from  each  other,  and 
called  valvula  conniventes.  Npw  this  disposi- 
tion will  be  found  to  afford  a farther  proof  of 
that  divine  wisdom,  which  the  anatomist  and 
physiologist  cannot  fail  to  discover  in  all  their 
pursuits. — For  if  the  intestinal  canal  was  much 
shorter  than  it  naturally  is ; if  instead  of  the 
present  circumvolutions  it  passed  in  a direct 
course  from  the  stomach  ; and  if  its  inner  sur- 
face was  smooth  and  destitute  of  valves  ; the 
aliment  would  consequently  pass  with  great  ra- 
pidity to  the  anus,  and  sufficient  time  would  be 
wanting  to  assimilate  the  chyle,  and  for  the  ne- 
cessary absorption  of  it  into  the  lacteals  : so 
that  the  body  would  be  deprived  of  the  supply 
of  nutrition,  which  is  so  essential  to  life  and 
health  ; but  the  length  and  circumvolutions  of 


278 


Of  the  Abdomen. 


the  intestines,  the  inequality  of  their  internal 
surface,  and  the  course  of  the  aliment  through 
them,  all  concur  to  perfect  the  separation  of 
the  chyle  from  the  fasces,  and  to  afford  the  ne- 
cessary nourishment  to  the  body. 

Sect.  XIV.  Of  the  Course  of  the  Chyle , and 
of  the  Lymphatic  System. 

An  infinite  number  of  very  minute  vessels, 
called  the  lacteal  veins , arise  like  net-work  from 
the  inner  surface  of  the  intestines,  (but  princi- 
pally from  the  jejunum  and  ilium),  which  are 
distended  to  imbibe  the  nutritious  fluid  or 
chyle.  These  vessels,  which  were  discovered 
by  Asellius  in  1622,  * pass  obliquely  through 
the  coats  of  the  intestine,  and  running  along 
the  mesentery,  unite  as  they  advance,  and  form 
larger  branches,  all  of  which  pass  through  the 
mesenteric  or  conglobate  glands,  which  are  ve- 
ry numerous  in  the  human  subject.  As  they 

* We  are  informed  by  Galen,  that  the  lacteals  had  been  seen 
in  kids  by  Erasistratus,  who  considered  them  as  arteries  carrying 
a milky  fluid  : but  from  the  remote  time  in  which  he  lived,  they 
do  not  seem  to  have  been  noticed  till  they  were  discovered  in  a 
living  dog  by  Asellius,  who  denominated  them  lacteals,  and  con- 
sidered them  as  serving  to  convey  the  chyle  from  the  intestines  to 
the  liver  ; for  before  the  discovery  of  the  thoracic  duft,  the  use 
of  the  liver  was  universally  supposed  to  be  that  of  converting  the 
chyle  into  blood.  But  the  discovery  of  the  thoracic  duct  by  Pec- 
quet, not  long  after,  corrected  this  error.  Pecquet  very  candidly 
confesses,  that  this  discovery  accidentally  arose  from  his  observ- 
ing a white  fluid,  mixed  with  the  blood,  flowing  out  of  the  vena 
cava,  after  he  had  cut  off  the  heart  of  a living  dog  ; which  he  sus- 
pected to  be  chyle,  and  afterwards  traced  to  its  source  from  the 
thoracic  duct : this  duct  had  been  seen  near  an  hundred  years  be- 
fore in  a horse  by  Eustachius,  who  speaks  of  it  as  a vein  of  a 
particular  structure,  but  without  knowing  any  thing  of  its  termi- 
nation or  use. 


279 


Of  the  Abdomen. 

run  between  the  intestines  and  these  glands, 
they  are  styled  vena;  lactea  primi  generis : but 
after  leaving  these  glands,  they  are  found  to  be 
less  numerous,  and  being  increased  in  size,  are 
then  called  vena  lactea  secundi  generis , which 
go  to  deposite  their  contents  in  the  thoracic  duct , 
through  which  the  chyle  is  conveyed  into  the 
blood. 

This  thoracic  duct  begins  about  the  lower 
part  of  the  first  vertebra  lumborum,  from 
whence  it  passes  up  by  the  side  of  the  aorta, 
between  that  and  the  vena  azygos,  close  to  the 
vertebrae,  being  covered  by  the  pleura.  Some- 
times it  is  found  divided  into  two  branches  ; but 
they  usually  unite  again  into  one  canal,  which 
opens  into  the  left  subclavian  vein,  after  having 
run  a little  way  in  an  oblique  course  between 
its  coats.  The  subclavian  vein  communicates 
with  the  vena  cava,  which  passes  to  the  right 
auricle  of  the  heart. 

The  lower  part  of  this  duct  being  usually  larg- 
er than  any  other  part  of  it,  has  been  named 
receptaculum  chyli , or  Pecquet's  receptacle  in 
honour  of  the  anatomist  who  first  discovered 
it  in  16  51.  In  some  quadrupeds,  in  turtle  and 
in  fish,  this  enlargement  * is  more  considera- 
ble in  proportion  to  the  size  of  the  duct,  than  it 
usually  is  in  the  human  subject,  where  it  is  not 
commonly  found  large  enough  to  merit  the 
name  of  receptaculum. 

Opportunities  of  observing  the  lacteals  in 
the  human  subject  do  not  often  occur;  but 
they  may  be  easily  demonstrated  in  a dog  or 


* Hewson’s  Exp.  Inq.  Part  Ii. 


280 


Of  the  Abdomen. 

any  other  quadruped  that  is  killed  two  or  three 
hours  after  feeding  upon  milk,  for  then  they 
appear  filled  with  white  chyle. 

But  these  Icicteals  which  we  have  described,  as 
passing  from  the  intestines  through  the  mesen- 
tery to  the  thoracic  duct,  compose  only  a part 
of  a system  of  vessels  which  perform  the  of- 
fice of  absorption , and  which  constitute,  with 
their  common  trunk  the  thoracic  duct,  and  the 
conglobate  glands  that  are  dispersed  through 
the  body,  what  may  be  styled  the  lymphatic 
system.  So  that  what  is  said  of  the  structure 
of  one  of  these  series  of  vessels  may  very 
properly  be  applied  to  that  of  the  other. 

The  lymphatic  veins*  are  minute  pellucid 
tubes,  which,  like  the  lacteals,  direct  their 
course  towards  the  centre  of  the  body,  where 
they  pour  a colourless  fluid  into  the  thoracic 
duct.  The  lymphatics  from  all  the  lower  parts 
of  the  body  gradually  unite  as  they  approach 
this  duct,  into  which  they  enter  by  three  or 
four  very  large  trunks,  that  seem  to  form  the 
lower  extremity  of  this  canal,  or  receptaculum 

* The  arteries  in  their  course  through  the  body  becoming  gra- 
dually too  minute  to  admit  the  red  globules  of  the  blood,  have 
then  been  styled  capillary  or  lymphatic  arteries.  The  vessels  which 
are  here  described  as  constituting  the  lymphatic  system,  were  at 
first  supposed  to  be  continued  from  those  arteries,  and  to  convey 
back  thelvmph,  either  into  the  red  veins  or  the  thoracic  duct ; the 
office  of  absorption  having  been  attributed  to  the  red  veins.  But 
we  know  that  the  lymphatic  veins  are  not  continuations  of  the  lym- 
phatic arteries, but  that  they  constitute  the  absorbent  system.  There  are 
still,  however,  some  very  respectable  names  among  the  anatomists 
of  the  present  age,  who  contend,  that  the  red  veins  act  likewise 
as  absorbents  : — but  it  seems  to  have  been  clearly  proved,  that  the 
red  veins  do  absorb  nowhere  but  in  the  cavernous  cells  of  the 
penis,  the  erection  of  which  is  occasioned  by  a distention  of  those 
cells  with  arterial  blood, 


281 


Of  the  Abdomen . 

chyli,  which  may  be  considered  as  the  great 
trunk  of  the  lymphatic  system.  The  lacteals 
open  into  it  near  the  same  place  ; and  the  lym- 
phatics, from  a large  share  of  the  upper  parts 
of  the  body,  pour  their  lymph  into  different 
parts  of  this  duct  as  it  runs  upwards,  to  termi- 
nate in  the  left  subclavian  vein.  The  lympha- 
tics from  the  right  side  of  the  neck,  thorax,  and 
right  arm,  £kc.  terminate  in  the  right  subclavi- 
an vein. 

As  the  lymphatics  commonly  lie  close  to  the 
large  blood-vessels,  a ligature  passed  round 
the  crural  artery  in  a living  animal,  by  includ- 
ing the  lymphatics,  will  occasion  a distention 
of  these  vessels  below  the  ligature,  so  as  to  de- 
monstrate them  with  ease  ; and  a ligature  pass- 
ed round  the  thoracic  duct,  instantly  after  kill- 
ing an  animal,  will,  by  stopping  the  course  of  its 
contents  into  the  subclavian  vein,  distend  not 
only  the  lacteals,  but  also  the  lymphatics  in  the 
abdomen  and  lower  extremities,  with  their  na- 
tural fluids.  * 

The  coats  of  these  vessels  are  too  thin  to  be 
separated  from  each  other  ; but  the  mercury 
they  are  capable  of  sustaining,  proves  them  to 
be  very  strong ; and  their  great  power  of  con- 
traction, after  undergoing  considerable  disten- 
tion, together  with  the  irritability  with  which 
Baron  Haller  found  them  to  be  enduedf,  seems 

N n 

* In  the  dead  body  they  may  be  easily  demonstrated  by  open- 
ing the  artery  ramifying  through  any  viscus,  as  in  the  spleen, 
for  instance,  and  then  throwing  in  air  ; by  which  the  lymphatics 
will  be  distended.  One  of  them  may  then  be  punctured,  and 
mercury  introduced  into  it  through  a blow-pipe. 

t Sur  le  movement  du  sang  Ex.  295,  298. 


282 


Of  the  Abdomen. 


to  render  it  probable,  that,  like  the  blood-ves- 
sels, they  have  a muscular  coat. 

The  lymphatics  are  nourished  after  the  same 
manner  as  all  the  other  parts  of  the  body.  For 
even  the  most  minute  of  these  vessels  are  pro- 
bably supplied  with  still  more  minute  arteries 
and  veins.  This  seems  to  be  proved  by  the 
inflammation  of  which  they  are  susceptible  ; 
and  the  painful  swellings  which  sometimes 
take  place  in  lymphatic  vessels,  prove  that 
they  have  nerves  as  well  as  blood-vessels. 

Both  the  lacteals,  lymphatics,  and  thoracic 
duct,,  are  furnished  with  valves,  which  are 
much  more  common  in  these  vessels  than  in 
the  red  veins.  These  valves  are  usually  in 
pairs,  and  serve  to  promote  the  course  of  the 
chyle  and  lymph  towards  the  thoracic  duct,  and 
to  prevent  its  return.  Mention  has  been  made 
of  the  glands,  through'  which  the  lacteals  pass 
in  their  course  through  the  mesentery ; and  it 
is  to  be  observed,  that  the  lymphatics  pass 
through  similar  glands  in  their  way  to  the  tho- 
racic duct.  These  glands  are  all  of  a conglo- 
bate kind,  but  the  changes  which  the  chyle  and 
lymph  undergo  in  their  passage  through  them,, 
have  not  yet  been  ascertained. 

The  lymphatic  vessels-  begin  from  surfaces 
and  cavities  in  all  parts  of  the  body  as  absorb - 
ents.  This  is  a fact  now  universally  allowed ; 
but  how  the  fluids  they  absorb  are  poured  into 
those  cavities,  is  a subject  of  controversy.  The 
contents  of  the  abdomen,  for  instance,  were 
described  as  being  constantly  moistened  by  a 
very  thin  watery  fluid.  The  same  thing  takes 
place  in  the  pericardium,  pleura,,  and  all  the 


283 


Of  the  Abdomen. 

e>ther  cavities  of  the  body,  and  this  watery  flu- 
id is  the  lymph.  But  whether  it  is  exhaled  into 
those  cavities  through  the  minute  ends  of  arte- 
ries, or  transuded  through  their  coats,  are  the 
points  in  dispute.  We  cannot  here  be  permit- 
ted to  relate  the  many  ingenious  arguments 
that  have  been  advanced  in  favour  of  each  of 
these  opinions  ; nor  is  it  perhaps  of  conse- 
quence to  our  present  purpose  to  enter  into  the 
dispute.  It  will  be  sufficient  if  the  reader  can 
form  an  idea  of  what  the  lymph  is,  and  . of  the 
manner  in  which  it  is  absorbed. 

The  lymph , from  its  transparency  and  want 
of  colour,  would  seem  to  be  nothing  but  wa- 
ter; and  hence  the  first  discoverers  of  these 
vessels  styled  them  ductus  aquosi : but  experi- 
ments prove,  that  the  lymph  of  an  healthy  ani- 
mal coagulates  by  being  exposed  to  the  air, 
or  a certain  degree  of  heat,  and  likewise  by  be- 
ing suffered  to  rest ; seeming  to  agree  in  this 
property  with  that  part  of  the  blood  called  the 
coagulcible  lymph. — This  property  of  the  lymph 
leads  to  determine  its  use,  in  moistening  and 
lubricating  the  several  cavities  of  the  body  in 
which  it  is  found;  and  for  which,  by  its  gela- 
tinous principle,  it  seems  to  be  much  better 
calculated  than  a pure  and  watery  fluid  would 
be,  for  such  it  has  been  supposed  to  be  by 
some  anatomists. 

The  mouths  of  the  lymphatics  and  lactecds , by 
acting  as  capillary  tubes,  seem  to  absorb  the 
lymph  and  chyle  somewhat  in  the  same  manner 
as  a capillary  tube  of  glass,  when  put  into  a ba- 
son of  water,  is  enabled  to  attract  the  water  into 
it  to  a certain  height ; but  it  is  probable  that  they 


284  Of  the  Abdomen. 

likewise  possess  a living  power,  which  assists 
in  performing  this  office.  In  the  human  body 
the  lymph , or  the  chyle , is  probably  conveyed 
upon  this  principle  as  far  as  the  first  pair  of 
valves,  which  seem  to  be  placed  not  far  from 
the  orifice  of  the  absorbing  vessel,  whether 
lymphatic  or  lacteal ; and  the  fluid  will  then  be 
propelled  forwards,  by  a continuation  of  the 
absorption  at  the  orifice.  But  this  does  not 
seem  to  be  the  only  inducement  to  its  progress 
towards  the  thoracic  duct ; these  vessels  have 
probably  a muscular  coat,  which  may  serve  to 
press  the  fluid  forwards  from  one  pair  of  valves 
to  another  ; and  as  the  large  lymphatic  vessels 
and  the  thoracic  duct  are  placed  close  to  the 
large  arteries,  which  have  a considerable  pul- 
sation, it  is  reasonable  to  suppose,  that  they 
derive  some  advantages  from  this  situation. 

Sect.  XV.  Of  the  Generative  Organs  ; of 
Conception , &c. 

$.  1.  The  Male  Organs. 

The  male  organs  of  generation  have  been 
usually  divided  into  the  parts  which  serve  to 
prepare  the  semen  from  the  blood,  and  those 
which  are  distended  to  convey  it  into  the  womb. 
But  it  seems  to  be  more  proper  to  distinguish 
them  into  the  preparing , the  containing , and 
the  expelling  parts,  which  are  the  different 
offices  of  the  testes , the  vesiculce  seminales , and 
the  penis  ; and  this  is  the  order  in  which  we 
propose  to  describe  them. 


285 


Of  the  Abdomen. 

The  testes  are  two  glandular  bodies,  serving 
to  secrete  the  semen  from  the  blood.  They 
are  originally  formed  and  lodged  within  the  ca- 
vity of  the  abdomen ; and  it  is  not  till  after 
the  child  is  born,  or  very  near  that  time,  that 
they  begin  to  pass  into  the  groin,  and  from 
thence  into  the  scrotum.*  By  this  disposition 
they  are  very  wisely  protected  from  the  inju- 
ries to  which  they  would  be  liable  to  be  ex- 
posed, from  the  different  positions  of  the  child 
at  the  time  of  parturition. 

The  testicles  in  this  state  are  loosely  at- 
tached to  the  psose  muscles,  by  means  of  the 
peritonaeum  by  which  they  are  covered ; and 
they  are  at  this  time  of  life  connected  in  a 
very  particular  manner  to  the  parietes  of  the 
abdomen,  and  likewise  to  the  scrotum,  by 
means  of  a substance  which  Mr.  Hunter  calls 
the  ligament  or  gubernaculum  testis , because  it 
connects  the  testis  with  the  scrotum,  and  di- 
rects its  course  in  its  descent.  This  guber- 


* It  sometimes  happens  in  dissecting  ruptures,  that  the  intes- 
tine is  found  in  the  same  sac,  and  in  contact  with  the  testis. 
This  appearance  was  at  first  attributed  to  a supposed  laceration 
of  the  peritonaeum  ; but  later  observations,  by  pointing  out  the 
situation  of  the  testicles  in  the  foetus,  have  led  to  prove,  that 
the  testis,  as  it  descends  into  the  scrotum,  carries  with  it  a por- 
tion or  elongation  of  the  peritonaeum,  which  becomes  its  tunica 
vaginalis,  or  a kind  of  sac,  in  which  the  testicle  is  lodged,  as 
will  be  explained  in  the  course  of  this  section.  The  communica- 
tion between  this  sac  and  the  cavity  of  the  abdomen,  is  usually 
soon  cut  off ; but  in  some  subjects  it  continues  open  during  life  $ 
and  when  an  hernia  or  descent  of  the  intestine  takes  place  in  such 
a subject,  it  does  not  push  down  a portion  of  the  peritonaeum 
before  it,  as  it  must  otherwise  necessarily  do,  but  passes  at  once 
through  this  opening,  and  comes  in  contact  with  tire  naked  tes- 
ticle, constituting  that  particular  species  of  rupture  called  hernia 
congenita. 


286  Of  the  Abdomen. 

naculum  is  of  a pyramidal  form,  with  its  bul- 
bous head  fixed  to  the  lower  end  of  the  testis 
and  epididymis,  and  loses  its  lower  and  slen- 
der extremity  in  the  cellular  membrane  of  the 
scrotum.  It  is  difficult  to  ascertain  what  the 
structure  and  composition  of  this  gubernacu- 
lum  is,  but  it  is  certainly  vascular  and  fibrous  ; 
and,  from  certain  circumstances,  it  would  seem 
to  be  in  part  composed  of  the  cremaster  mus- 
cle, running  upwards  to  join  the  lower  end 
of  the  testis. 

We  are  not  to  suppose  that  the  testicle, 
when  descended  into  the  scrotum,  is  to  be 
seen  loose  as  a piece  of  gut  or  omentum 
would  be  in  a common  hernial  sac.  We  have 
already  observed,  that  during  its  residence  in 
the  cavity  of  the  abdomen  it  is  attached  to  the 
peritoneum,  which  descends  with  it ; so  that 
when  the  sac  is  completed  in  the  scrotum,  the 
testicle  is  at  first  attached  only  to  the  posterior 
part  of  it,  while  the  fore  part  of  it  lies  loose, 
and  for  some  time  affords  a communication 
with  the  abdomen.  The  spermatic  chord., 
which  is  made  up  of  the  spermatic  artery  and 
vein,  and  of  the  vas  deferens  or  excretory  duct 
of  the  testis,  is  closely  attached  behind  to  the 
posterior  part  of  this  elongation  of  the  perito- 
naeum- But  the  fore  part  of  the  peritoneal 
sac,  which  is  at  first  loose  and  not  attached  to 
the  testicle,  closes  after  a certain  time,  and 
becomes  united  to  the  posterior  part,  and  thus 
perfectly  surrounds  the  testicle  as  it  were  in 
a purse. 

The  testicles  of  the  foetus  differ  only  in  their 
size  and  situation  from  those  of  the  adult.  In 


Of  the  Abdomen. 


28Z 


their  passage  from  the  abdomen  they  descend 
through  the  abdominal  rings  into  the  scrotum, 
where  they  are  supported  and  defended  by  va- 
rious integuments. 

What  the  immediate  cause  of  this  descent 
is,  has  not  yet  been  satisfactorily  determined. 
It  has  been  ascribed  to  the  effects  of  respira- 
tion, but  the  testicles  have  sometimes  been 
found  in  the  scrotum  before  the  child  has 
breathed;  and  it  does  not  seem  to  be  occasi- 
oned by  the  action  of  the  cremaster  muscle, 
because  the  same  effect  would  be  liable  to 
happen  to  the  hedge-hog,  and  some  other 
quadrupeds,  whose  testicles  remain  in  the  ab- 
domen during  life. 

The  scrotum,  which  is  the  external  or  com- 
mon covering  of  both  testicles,  is  a kind  of  sac 
formed  by  the  common  integuments,  and  ex- 
ternally divided  into  two  equal  parts  by  a pro- 
minent line  called  raphe. 

In  the  inner  part  of  the  scrotum  we  meet 
with  a cellular  coat  called  dart-os ,*  which  by 
its  duplieature  divides  the  scrotum  into  two- 
equal  parts,  and  forms  what  is  called  septum 
scroti , which  corresponds  with  the  raphe. 
The  collapsion  which  is  so  often  observed  to 
take  place  in  the  scrotum  of  the  healthy  sub- 
ject, when  excited  by  cold  or  by  the  stimulus 
of  venery,  seems  to  be  very  properly  attribut- 

* The  dartos  has  usually  been  considered  as  a muscle,  and  is 
described  as  such  both  by  Douglas  and  Winslow.  But  there 
iaeing  no  part  of  the  scrotum  of  the  human  subject  which  can  be- 
to  consist  of  muscular  fibres,  Albinus  and  Haller  have  very 
^^perly  omitted  to  describe  the  dartos  as  a muscle,  and  consider 
it  merelv  as  a cellular  coat. 


28S 


Of  the  Abdomen. 


ed  to  the  contractile  motion  of  the  skin,  and 
not  to  any  muscular  fibres,  as  is  the  case  in 
dogs  and  some  other  quadrupeds. 

The  scrotum,  then,  by  means  of  its  septum, 
is  found  to  make  two  distinct  bags,  in  which 
the  testicles,  invested  by  their  proper  tunics, 
are  securely  lodged  and  separated  from  each 
other.  These  coats  are  the  cremaster,  the 
tunica  vaginalis,  and  the  tunica  albuginea. 
The  first  of  these  is  composed  of  muscular 
fibres,  and  is  to  be  considered  only  as  a par- 
tial covering  of  the  testis  ; for  it  surrounds 
only  the  spermatic  chord,  and  terminates  upon 
the  upper  and  external  parts  of  the  tunica  va- 
ginalis testis,  serving  to  draw  up  and  suspend 
the  testicle.*  The  tunica  vaginalis  testis  has 
already  been  described  as  being  a thin  pro- 
duction of  the  peritonaeum,  loosely  adhering 
every  where  to  the  testicle,  which  it  includes 
as  it  were  in  a bag.  The  tunica  albuginea  is 
a firm,  white,  and  very  compact  membrane 
of  a glistening  appearance,  which  immediate- 
ly invests  the  body  of  the  testis  and  the  epidi- 
dymus  ; serving  in  some  measure  to  connect 
them  to  each  other,  but  without  extending 
itself  at  all  to  the  spermatic  chord.  This  tu- 
nica albuginea  serves  to  confine  the  growth 
of  the  testis  and  epididymus  within  certain 
limits,  and  by  giving  them  a due  degree  of 
firmness,  enables  them  to  perform  their  pro- 
per functions. 

* The  cremaster  muscle  is  composed  of  a few  fibres  from  the 
obliquus  internus  abdominis,  which  uniting  with  a few  from  the 
transversalis,  descend  upon  the  spermatic  chord,  and  are  insen- 
sibly lost  upon  the  tunica  vaginalis  of  the  testicle.  It  serves  to 
suspend  and  draw  up  the  testicle. 


289 


Of  the  Abdomen • 

Having  removed  this  last  tunic,  we  disco- 
ver the  substance  of  the  testicle  itself,  which 
appears  to  be  made  up  of  an  infinite  number 
of  very  elastic  filaments,  which  may  be  best 
distinguished  after  macerating  the  testicle  in 
water.  Each  testicle  is  made  up  of  the  sper- 
matic artery  and  vein,  and  the  excretory  ves- 
sels or  tubuli  seminiferi.  There  are  likewise 
a great  number  of  absorbent  vessels,  and  some 
branches  of  nerves  to  be  met  with  in  the  tes- 
ticles. 

The  spermatic  arteries  arise  one  on  each 
side  from  the  aorta,  generally  about  an  inch 
below  the  emulgents.  The  right  spermatic 
vein  commonly  passes  into  the  vena  cava ; but 
the  left  spermatic  vein  usually  empties  itself 
into  the  emulgent  on  that  side ; and  it  is  sup- 
posed to  take  this  course  into  the  emulgent, 
that  it  may  avoid  passing  over  the  aorta,  which 
it  would  be  obliged  to  do  in  its  way  to  the 
vena  cava. 

The  blood  is  circulated  very  slowly  through 
the  spermatic  artery,  which  makes  an  infinite 
number  of  circumvolutions  in  the  substance  of 
the  testicle,  where  it  deposites  the  semen, 
which  passes  through  the  tubuli  seminiferi. 
These  tubuli  seminiferi  are  seen  running  in 
short  waves  from  the  tunica  albuginea  to  the 
axis  of  the  testicle  ; and  are  divided  into  dis- 
tinct portions  by  certain  thin  membranous  pro- 
ductions, which  originate  from  the  tunica  al- 
buginea. They  at  length  unite,  and  by  an 
infinite  number  of  convolutions  form  a sort  of 

O o 


290 


Of  the  Abdomen. 


appendix  to  the  testis  called  epididymis ,*  which 
is  a Vascular  body  of  an  oblong  shape,  situate 
upon  the  superior  part  of  each  testicle.  These 
tubuli  of  the  epididymis  at  length  form  an  ex- 
cretory duct  called  vas  deferens , which  as- 
cends towards  the  abdominal  rings,  with  the 
other  parts  that  make  up  the  spermatic  chord, 
and  then  a separation  takes  place ; the  nerves 
and  blood-vessels  passing  on  to  their  several 
terminations,  and  the  vas  deferens  going  to 
deposite  its  semen  in  the  vesiculse  seminales, 
which  are  two  soft  bodies  of  a white  and  con- 
voluted appearance  externally,  situated  ob- 
liquely between  the  rectum  and  the  lower 
part  of  the  bladder,  and  uniting  together  at 
the  lower  extremity.  From  these  reservoirs, t 

* The  testicles  were  named  didymi  by  the  ancients,  and  the 
name  of  this  part  was  given  to  it  on  account  of  its  situation  upon 
the  testicle. 

-j-  That  the  bags  called  veskula  seminalts  are  reservoirs  of  se- 
men, is  a circumstance  which  has  been  by  anatomists  universal- 
ly believed.  Mr.  J.  Hunter,  however,  from  several  circumstan- 
ces, has  been  induced  to  think  this  opinion  erroneous. 

He  has  examined  these  vesiculae  in  people  who  have  died  sud- 
denly, and  he  found  their  contents  to  be  different  in  their  proper- 
ties from  the  semen.  In  those  who  had  lost  one  of  the  testicles, 
or  the  use  of  one  of  them,  by  disease,'  both  the  vesiculae  were 
full,  and  their  contents  similar.  And  in  a lusus  nature,  where 
there  was  no  communication  between  the  vasa  deferentia  and  ve- 
siculse, nor  between  the  vesiculse  and  penis,  the  same  thing  took 
place. 

From  these  observations,  he  thinks  we  have  a presumptive 
proof,  That  the  semen  can  be  absorbed  in  the  body  of  the  testi- 
cle and  in  the  epididymis,  and  that  the  vesiculae  secrete  a mucus 
which  they  are  capable  of  absorbing  when  it  cannot  be  made  use 
of : That  the  semen  is  not  retained  in  reservoirs  after  it  is  secret- 
ed, and  kept  there  till  it  is  used;  but  that  it  is  secreted  at  the 
time,  in  consequence  of  certain  affections  of  tire  mind  stimulat- 
ing the  testicles  to  this  action. 

He  corroborates  his  observations  by  the  appearance  on  dissec- 
tion in  other  animals ; and  here  he  finds,  That  the  shape  and 


291 


Of  the  Abdomen. 

which  are  plentifully  supplied  with  blood-ves- 
sels and  nerves,  the  semen  is  occasionally  dis- 
charged through  two  short  passages,  which 
open  into  the  urethra  close  to  a little  eminence 
called  verumontamim. 

contents  of  the  vesiculae  vary  much  in  different  animals,  while 
the  semen  in  most  of  them  he  has  examined  is  nearly  the  same  ; 
That  the  vasa  deferentia  in  many  animals  do  not  communicate 
with  the  vesiculae : That  the  contents  of  the  vesiculae  of  castrated 
and  perfect  animals  are  similar,  and  nearly  equal  in  quantity,  in 
no  way  resembling  the  semen  as  emitted  from  the  animal  in 
coitu,  or  what  is  found  in  the  vas  deferens  after  death.  He  ob- 
serves likewise,  that  the  bulb  of  the  urethra  of  perfect  males  is 
considerably  larger  than  in  castrated  animals. 

From  the  whole,  he  thinks  the  following  inferences  may  be 
fairly  drawn : That  the  bags  called  vesicuU  seminales  are  not  se- 
minal reservoirs,  but  glands  secreting  a peculiar  mucus ; and 
that  the  bulb  of  the  urethra  is  properly  speaking  the  receptacle 
of  the  semen,  in  which  it  is  accumulated  previous  to  ejection. 

But  although  he  has  endeavoured  to  prove  that  the  vesiculae 
do  not  contain  the  semen,  he  has  not  been  able  to  ascertain  their 
particular  use.  He  thinks,  however,  we  may  be  allowed  upon 
the  whole  to  conclude,  that  they  are,  together  with  other  parts, 
subservient  to  tire  purposes  of  generation. 

Although  the  author  has  treated  this  subject  very  ably,  and 
made  many  ingenious  observations,  some  things  may  be  object- 
ed  to  what  he  has  advanced ; of  which  the  following  are  a few  : 
That  those  animals  who  have  bags  called  vesical*  seminales  per- 
form copulation  quickly  ; whereas  others  that  want  them,  as  in 
the  dog  kind,  are  tedious  in  copulation:  That  in  tire  human 
body,  at  least,  there  is  a free  communication  between  the  vasa 
deferentia  and  vesiculae ; and  in  animals  where  the  author  has 
observed  no  communication  between  the  vasa  deferentia  and  ve- 
siculae, there  may  be  a communication  by  vessels  not  yet  disco- 
vered, and  which  may  be  compared  to  the  hepato-cystic  ducts 
in  fowls  and  fishes : That  the  fluid  in  the  end  of  the  vasa  defe- 
rentia and  the  vesiculae  seminales  are  similar,  according  to  the 
author’s  own  observation : That  the  vesiculae  in  some  animals 
increase  and  decrease  with  the  testicle  at  particular  seasons : 
That  in  birds  and  certain  fishes,  there  is  a dilatation  of  the  ends 
of  the  vasa  deferentia,  which  the  author  himself  allows  to  be  a 
reservoir  for  the  semen. 

With  respect  to  the  circumstance  of  the  bulb  of  the  urethra 
answering  the  purpose  of  a reservoir,  the  author  has  mentioned 
no  facts  which  tend  to  establish  this  opinion.  See  Observations 
on  certain  Parts  of  the  minimal  0 economy. 


292  Of  the  Abdomen. 

Near  this  eminence  we  meet  with  the  pros- 
tate, which  is  situated  at  the  neck  of  the  blad- 
der, and  is  described  as  being  of  a glandular 
structure.  It  is  shaped  somewhat  like  a heart 
with  its  small  end  foremost,  and  invests  the 
origin  of  the  urethra.  Internally  it  appears  to 
be  of  a firm  substance,  and  composed  of  seve- 
ral follicles,  secreting  a whitish  viscid  fluid, 
that  is  discharged  by  ten  or  twelve  excretory 
ducts  into  the  urethra,  on  each  side  of  the 
openings  of  the  vesicuke  seminales  at  the  same 
time,  and  from  the  same  causes  that  the  semen 
is  expelled.  As  this  latter  fluid  is  found  to  be 
exceedingly  limpid  in  the  vesiculae  seminales 
of  the  dead  subject,  it  probably  owes  its  white- 
ness and  viscidity  to  this  liquor  of  the  pros- 
tate. 

The  penis,  which  is  to  be  considered  as 
the  vehicle  or  active  organ  of  procreation,  is 
composed  of  two  columns,  the  corpora  caver- 
nosa, and  corpus  spongiosum.  The  corpora 
cavernosa,  which  constitute  the  greatest  part 
of  the  penis,  may  be  described  as  two  cylin- 
drical ligamentous  tubes,  each  of  which  is 
composed  of  an  infinite  number  of  minute  cells 
of  a spongy  texture,  which  communicate  with 
each  other.  These  two  bodies  are  of  a very 
pliant  texture,  and  capable  of  considerable 
distention;  and  being  united  laterally  to  each 
other,  occasion  by  this  union  a space  above 
and  another  below.  The  uppermost  of  these 
spaces  is  filled  by  the  blood-vessels,  and  the 
lower  one,  which  is  larger  than  the  other,  by 
the  urethra  and  its  corpus  spongiosum.  These 
two  cavernous  bodies  are  at  first  only  separat- 


295 


Of  the  Abdomen. 

ed  by  a partition  of  tendinous  fibres,  which 
allow  them  to  communicate  with  each  other ; 
but  they  afterwards  divaricate  from  each  other 
like  the  branches  of  the  letter  Y,  and  diminish- 
ing gradually  in  size,  are  attached,  one  on 
each  side,  by  means  of  the  ligamentum  sus- 
pensorium  penis  to  the  ramus  ischii,  and  to 
the  inferior  portion  of  the  os  pubis. 

The  corpus  spongiosum  penis,  or  corpus 
spongiosum  urethrse,  as  it  is  styled  by  some 
authors,  begins  as  soon  as  the  urethra  has 
passed  the  prostate,  with  a thick  origin  almost 
like  a heart,  first  under  the  urethra,  and  af- 
terwards above  it,  becoming  gradually  thin- 
ner, and  surrounding  the  whole  canal  of  the 
urethra,  till  it  terminates  in  a considerable  ex- 
pansion, and  constitutes  what  is  called  the 
glans  penis , which  is  exceedingly  vascular,  and 
covered  with  papillse  like  the  tongue.  The 
cuticle  which  lines  the  inner  surface  of  the  ure- 
thra, is  continued  over  the  glans  in  the  same 
manner  as  it  is  spread  over  the  lips. 

The  penis  is  invested  by  the  common  inte- 
guments, but  the  cutis  is  reflected  back  every 
where  from  the  glans  as  it  is  in  the  eye-lids  ; 
so  that  it  covers  this  part,  when  the  penis  is  in 
a relaxed  state,  as  it  were  with  a hood,  and 
from  this  use  is  called  prepuce. 

The  prepuce  is  tied  down  to  the  under  part 
of  the  glans  by  a small  ligament  called  franum, 
which  is  in  fact  only  a continuation  of  the  cu- 
ticle and  cutis.  There  are  many  simple  seba- 
ceous follicles  called  glandule  odorifera, 
placed  round  the  basis  of  the  glans  ; and  the 
fluid  they  secrete  serves  to  preserve  the  exqui- 


294 


Of  the  Abdomen. 

site  sensibility  of  this  part  of  the  penis,  and  to 
prevent  the  ill  effects  of  attrition  from  the  pre- 
puce. 

The  urethra  may  be  defined  to  be  a mem- 
branous canal,  passing  from  the  bladder 
through  the  whole  extent  of  the  penis,  Seve- 
ral very  small  openings,  called  lacuna , com- 
municate with  this  canal,  through  which  a mu- 
cus is  discharged  into  it ; and  besides  these, 
there  are  two  glands,  first  described  by  Cow- 
per,  as  secreting  a fluid  for  lubricating  the 
urethra,  and  called  Cowper's  glands  •*  and 
Littref  speaks  of  a gland  situated  near  the 
prostate,  as  being  destined  for  the  same  use. 

The  urethra  being  continued  from  the  neck 
of  the  bladder,  is  to  be  considered  as  making 
part  of  the  urinary  passage ; and  it  likewise 
affords  a conveyance  to  the  semen,  which  we 
have  observed  is  occasionally  discharged  into 
it  from  the  vesiculse  seminales.  The  direc- 
tion of  this  canal  being  first  under  and  then 
before  the  pubis,  occasions  a winding  in  its 
course  from  the  bladder  to  the  penis  not  unlike 
the  turns  of  the  letter  S. 

The  penis  has  three  pair  of  muscles,  the 
erectores,  acceleratores,  and  transversales. 
They  push  the  blood  from  the  crura  to  the  fore 
part  of  the  corpora  cavernosa.  The  first  origi- 
nate from  the  tuberosity  of  the  ischium,  and 
terminate  in  the  corpora  cavernosa.  The  ac- 
celeratores arise  from  the  sphincter,  and  by 

* Both  Heister  and  Morgagni  observe,  that  they  have  some- 
times not  been  able  to  find  these  glands  ; so  that  they  do  not 
seem  to  exist  in  all  subjects. 

+ Memoires  de  1’  Acad.  Royale  des  Sciences,  1700. 


295 


Of  the  Abdomen. 

their  insertion  serve  to  compress  the  bulbous 
part  of  the  urethra ; and  the  transversales  are 
destined  to  afford  a passage  to  the  semen,  by- 
dilating  the  canal  of  the  urethra. 

The  arteries  of  the  penis  are  chiefly  deriv- 
ed from  the  internal  iliacs.  Some  of  them  are 
supposed  to  terminate  by  pabulous  orifices 
within  the  corpora  cavernosa  and  corpus  spon- 
giosum ; and  others  terminate  in  veins,  which 
at  last  make  up  the  vena  magna  dorsi  penis, 
and  other  smaller  veins,  which  are  in  general 
distributed  in  like  order  with  the  arteries. 

Its  nerves  are  large  and  numerous.  They 
arise  from  the  great  sciatic  nerve,  and  accom- 
pany the  arteries  in  their  course  through  the 
penis. 

We  have  now  described  the  anatomy  of  this 
organ  ; and  there  only  remains  to  be  explain- 
ed, how  it  is  enabled  to  attain  that  degree  of 
firmness  and  distention  which  is  essential  to 
the  great  work  of  generation. 

The  greatest  part  of  the  penis  has  been 
spoken  of  as  being  of  a spongy  and  cellular 
texture,  plentifully  supplied  with  blood-vessels 
and  nerves,  and  as  having  muscles  to  move 
it  in  different  directions.  Now,  the  blood  is 
constantly  passing  into  its  cells  through  the 
small  branches  of  the  arteries  which  open  into 
them,  and  is  from  thence  as  constantly  return- 
ed by  the  veins,  so  long  as  the  corpora  caver- 
nosa and  corpus  spongiosum  continue  to  be  in 
a relaxed  and  pliant  state.  But  when,  from 
any  nervous  influence,  or  other  means,  which 
it  is  not  necessary  here  to  define  or  explain, 
the  erectores  penis,  ejaculatores  seminis,  le- 


296 


Of  the  Abdomen . 


vatores  ani,  btc.  are  induced  to  contract,  the 
veins  undergo  a certain  degree  of  compres- 
sion, and  the  passage  of  the  blood  through 
them  is  so  much  impeded,  that  it  collects  in 
them  in  a greater  proportion  than  they  are 
enabled  to  carry  off,  so  that  the  penis  gradu- 
ally enlarges  ; and  being  more  and  more  for- 
cibly drawn  up  against  the  os  pubis,  the  vena 
magna  itself  is  at  length  compressed,  and  the 
penis  becomes  fully  distended.  But  as  the 
causes  which  first  occasioned  this  distention 
subside,  the  penis  gradually  returns  to  its  state 
of  relaxation. 

§.  2.  Female  Organs  of  Generation. 

Anatomical  writers  usually  divide  the  fe- 
male organs  of  generation  into  external  and  in- 
ternal. In  the  first  division  they  include  the 
mons  veneris , labia  pudendi , perinaum , clito- 
ris, nymphce , and  caruncula  myrtiformes  ; and 
in  the  latter,  the  vagina , with  the  uterus  and 
its  appendages. 

The  mons  veneris , which  is  placed  on  the 
upper  part  of  the  symphysis  pubis,  is  inter- 
nally composed  of  adipose  membranes,  which 
makes  it  soft  and  prominent : it  divides  into 
two  parts  called  labia  pudendi,  which  descend- 
ing towards  the  rectum,  from  which  they  are 
divided  by  the  perinseum,  form  what  is  called 
the  fourchette.  The  perinseum  is  that  fleshy 
space  which  extends  about  an  inch  and  an  half 
from  the  fourchette  to  the  anus,  and  from 
thence  about  two  inches  to  the  coccyx. 


297 


Of  the  Abdomen. 

The  labia  pudendi  being  separated,  we  ob- 
serve a sulcus  called  fossa  magna  ; in  the  up- 
per part  of  which  is  placed  the  clitoris,  a small 
round  spongy  body,  in  some  measure  resem- 
bling the  male  penis,  but  impervious,  com- 
posed of  two  corpora  cavernosa,  arising  from 
the  tuberosities  of  the  ossa  ischii ; furnished 
with  two  pair  of  muscles,  the  erectores  clito- 
ridis,  and  the  sphincter  or  constrictor  ostii  va- 
ginas ; and  terminating  in  a glans,  which  is 
covered  with  its  prepuce.  From  the  lower 
part,  on  each  side  of  the  fossa,  pass  the  nym- 
phse,  two  membranous  and  spongy  folds  which 
seem  destined  for  useful  purposes  in  parturi- 
tion, by  tending  to  enlarge  the  volume  of  the 
vagina  as  the  child’s  head  passes  through  it. 
Between  these,  about  the  middle  of  the  fossa 
magna,  we  perceive  the  orifice  of  the  vagina  or 
os  externum,  closed  by  folds  and  wrinkles ; 
and  about  half  an  inch  above  this,  and  about 
an  inch  below  the  clitoris,  appears  the  meatus 
urinarius  or  orifice  of  the  urethra,  much  short- 
er, though  somewhat  larger,  than  in  men, 
with  a little  prominence  at  its  lower  edge, 
which  facilitates  the  introduction  of  the  ca- 
theter. 

The  os  externum  is  surrounded  internally 
by  several  membranous  folds  called  caruncul ce 
myrtiformes , which  are  partly  the  remains  of 
a thin  membrane  called  hymen , that  covers 
the  vagina  in  children.  In  general  the  hymen 
is  sufficiently  open  to  admit  the  passage  of  the 
menses,  if  it  exists  at  the  time  of  their  appear- 
ance ; sometimes,  however,  it  has  been  found 
perfectly  closed. 


pP 


298 


Of  the  Abdomen . 

The  vagina,  situated  between  the  urethra 
and  the  rectum,  is  a membranous  cavity,  sur- 
rounded especially  at  its  external  extremity 
with  a spongy  and  vascular  substance,  which 
is  covered  by  the  sphincter  ostii  vaginas.  It 
terminates  in  the  uterus,  about  half  an  inch 
above  the  os  tineas,  and  is  wider  and  shorter 
in  women  who  have  had  children  than  in  vir- 
gins. 

All  these  parts  are  plentifully  supplied  with 
blood-vessels  and  nerves.  Around  the  nym- 
phae  there  are  sebaceous  follicles,  which  pour 
out  a fluid  to  lubricate  the  inner  surface  of  the 
vagina ; and  the  meatus  urinarius,  like  the 
urethra  in  the  male  subject,  is  constantly 
moistened  by  a mucus,  which  defends  it  against 
the  acrimony  of  the  urine. 

The  uterus  is  a hollow  viscus,  situated  in 
the  hypogastric  region,  between  the  rectum 
and  bladder.  It  is  destined  to  receive  the  first 
rudiments  of  the  feetus,  and  to  assist  in  the 
developement  of  all  its  parts,  till  it  arrives  at 
a state  of  perfection,  and  is  fitted  to  enter  into 
the  world,  at  the  time  appointed  by  the  wise 
Author  of  nature. 

The  uterus,  in  its  unimpregnated  state,  re- 
sembles a pear  in  shape,  somewhat  flattened, 
with  its  fundus  or  bottom  part  turned  towards 
the  abdomen,  and  its  cervix  or  neck  surround- 
ed by  the  vagina.  The  entrance  into  its  ca- 
vity forms  a little  protuberance,  which  has 
been  compared  to  the  mouth  of  a tench,  and 
is  therefore  called  os  tinea. 

The  substance  of  the  uterus,  which  is  of  a 
considerable  thickness,  appears  to  be  com- 


Of  the  Abdomen.  299 

posed  of  muscular  and  small  ligamentous  fi- 
bres, small  branches  of  nerves,  some  lym- 
phatics, and  with  arteries  and  veins  innumera- 
ble. Its  nerves  are  chiefly  derived  from  the 
intercostal,  and  its  arteries  and  veins  from  the 
hypogastric  and  spermatic.  The  membrane 
which  lines  its  cervix,  is  a continuation  of  the 
inner  membrane  of  the  vagina  ; but  the  outer 
surface  of  the  body  of  the  uterus  is  covered 
with  the  peritonaeum,  which  is  reflected  over 
it,  and  descends  from  thence  to  the  intestinum 
rectum.  This  duplicature  of  the  peritonaeum, 
by  passing  off  from  the  sides  of  the  uterus  to 
the  sides  of  the  pelvis,  is  there  firmly  con- 
nected, and  forms  what  are  called  ligamento 
uteri  lata ; which  not  only  serve  to  support 
the  uterus,  but  to  convey  nerves  and  blood- 
vessels to  it. 

The  ligamenta  uteri  rotunda  arise  from  the 
sides  of  the  fundus  uteri,  and  passing  along 
within  the  fore-part  of  the  ligamenta  lata,  de- 
scend through  the  abdominal  rings,  and  ter- 
minate in  the  substance  of  the  mons  veneris. 
The  substance  of  these  ligaments  is  vascular, 
and  although  both  they  and  the  ligamenta  lata 
admit  the  uterus  in  the  virgin  state,  to  move 
only  about  an  inch  up  and  down,  yet  in  the 
course  of  pregnancy  they  admit  of  consider- 
able distention,  and  after  parturition  return 
nearly  to  their  original  state  with  surprising 
quickness. 

On  each  side  of  the  inner  surface  of  the 
uterus,  in  the  angle  near  the  fundus,  a small 
orifice  is  to  be  discovered,  which  is  the  begin- 
ning of  one  of  the  tubce  Fallopianas.  Each  of 


300 


Of  the  Abdomen. 


these  tubes,  which  are  two  in  number,  passing 
through  the  substance  of  the  uterus,  is  extend- 
ed along  the  broad  ligaments,  till  it  reaches  the 
edge  of  the  pelvis,  from  whence  it  reflects 
back;  and  turning  over  behind  the  ligaments, 
about  an  inch  of  its  extremity  is  seen  hanging 
loose  in  the  pelvis,  near  the  ovarium.  These 
extremities,  having  a jagged  appearance,  are 
called  fimbria , or  morsus  diaboli.  Each  tuba 
Fallopiana  is  usually  about  three  or  four  inches 
long.  Their  cavities  are  at  first  very  small, 
but  become  gradually  larger,  like  a trumpet, 
as  they  approach  the  fimbrise. 

Near  the  fimbriae  of  each  tuba  Fallopiana, 
about  an  inch  from  the  uterus,  is  situated  an 
oval  body  called  ovarium , of  about  half  the 
size  of  the  male  testicle.  Each  of  these  ovaria 
is  covered  by  a production  of  the  peritonaeum, 
and  hangs  loose  in  the  pelvis.  They  are  of  a 
flat  and  angular  form,  and  appear  to  be  com- 
posed of  a white  and  cellular  substance,  in 
which  we  are  able  to  discover  several  minute 
vesicles  filled  with  a coagulable  lymph,  of  an 
uncertain  number,  commonly  exceeding  12  in 
each  ovary.  In  the  female  of  riper  years, 
these  vesicles  become  exceedingly  turgid,  and 
a kind  of  yellow  coagulum  is  gradually  formed 
within  one  of  them,  which  increases  for  a cer- 
tain time.  In  conception,  one  of  these  mature 
ova  is  supposed  to  be  impregnated  with  the 
male  semen,  and  to  be  squeezed  out  of  its 
nidus  into  the  Fallopian  tube  ; after  which  the 
ruptured  part  forms  a substance  which  in  some 
animals  is  of  a yellow  colour,  and  is  therefore 
called  corpus  luteum ; and  it  is  observable,  that 


301 


Of  the  Abdomen. 

the  number  of  these  scars  or  fissures  in  the 
ovarium,  constantly  corresponds  with  the  num- 
ber of  foetuses  excluded  by  the  mother. 

§.3.  Of  Conception. 

Man,  being  ever  curious  and  inquisitive, 
has  naturally  been  led  to  inquire  after  the  origin 
of  his  existence  ; and  the  subject  of  generation 
has  employed  the  philosophical  world  in  all 
ages  : but  in  following  nature  up  to  her  mi- 
nute recesses,  the  philosopher  soon  finds  him- 
self bewildered,  and  his  imagination  often  sup- 
plies that  which  he  so  eagerly  wishes  to  disco- 
ver, but  which  is  destined  perhaps  never  to  be 
revealed  to  him.  Of  the  many  theories  which 
have  been  formed  on  this  subject,  that  of  the 
ancient  philosophers  seems  to  have  been  the 
most  simple  : they  considered  the  male  semen 
as  alone  capable  of  forming  the  fcetus,  and  be- 
lieved that  the  female  only  afforded  it  a lodging 
in  the  womb,  and  supplied  it  with  nourishment 
after  it  was  perfectly  formed.  This  opinion, 
however,  soon  gave  place  to  another,  in  which 
the  female  was  allowed  a more  considerable 
share  in  conception. 

This  second  system  considered  the  foetus 
as  being  formed  by  the  mixture  of  the  semi- 
nal liquor  of  both  sexes,  by  a certain  arrange- 
ment of  its  several  particles  in  the  uterus. 
But  in  the  16th  century,  vesicles  or  eggs  were 
discovered  in  the  ovaria  or  female  testicles  ; 
the  foetus  had  been  found  sometimes  in  the  ab- 
domen, and  sometimes  in  the  Fallopian  tubes ; 


302 


Of  the  Abdomen. 

and  the  two  former  opinions  were  exploded  in 
favour  of  a new  doctrine.  The  ovaria  were 
compared  to  a bunch  of  grapes,  being  suppos- 
ed to  consist  of  vesicles,  each  of  which  had  a 
stalk  ; so  that  it  might  be  disengaged  without 
hurting  the  rest,  or  spilling  the  liquor  it  con- 
tained. Each  vesicle  was  said  to  include  a lit- 
tle animal,  almost  complete  in  all  its  parts  ; and 
the  vapour  of  the  male  semen  being  conveyed 
to  the  ovarium,  was  supposed  to  produce  a fer- 
mentation in  the  vesicle,  which  approached 
the  nearest  to  maturity ; and  thus  inducing  it 
to  disengage  itself  from  the  ovarium,  it  passed 
into  the  tuba  Fallopiana,  through  which  it  was 
Conveyed  to  the  uterus.  Here  it  was  supposed 
to  take  root  like  a vegetable  seed,  and  to  form, 
with  the  vessels  originating  from  the  uterus, 
what  is  called  the  placenta  ; by  means  of  which 
the  circulation  is  carried  on  between  the  mo- 
ther and  the  foetus. 

This  opinion,  with  all  its  absurdities,  con- 
tinued to  be  almost  universally  adopted  till  the 
close  of  the  same  century,  when  Lieuwen- 
hoeck,  by  means  of  his  glasses,  discovered 
certain  opake  particles,  which  he  described  as 
so  many  animalcula,  floating  in  the  seminal 
fluid  of  the  male. 

This  discovery  introduced  a new  schism 
among  the  philosophers  of  that  time,  and  gave 
rise  to  a system  which  is  not  yet  entirely  explod- 
ed. According  to  this  theory  the  male  semen 
passing  into  the  tubas  Fallopianse,  one  of  the 
animalcula  penetrates  into  the  substance  of  the 
ovarium,  and  enters  into  one  of  its  vesicles  or 
ova.  This  impregnated  ovum  is  then  squeez- 


303 


Of  the  Abdomen. 

ed  from  its  husk,  through  the  coats  of  the  ova- 
rium, and  being  seized  by  the  fimbrise,  is  con- 
ducted through  the  tube  to  the  uterus,  where 
it  is  nourished  till  it  arrives  at  a state  of  per- 
fection. In  this  system  there  is  much  ingenu- 
ity ; but  there  are  certain  circumstances  sup- 
posed to  take  place,  which  have  been  hitherto 
inexplicable.  A celebrated  modern  writer,  M. 
BufFon,  endeavours  to  restore,  in  some  mea- 
sure, the  most  ancient  opinion,  by  allowing  the 
female  semen  a share  in  this  office  ; asserting, 
that  animalcula  or  organic  particles  are  to  be 
discovered  in  the  seminal  liquor  of  both  sexes  : 
he  derives  the  female  semen  from  the  ovaria, 
and  he  contends  that  no  ovum  exists  in  those 
parts.  But  in  this  idea  he  is  evidently  mista- 
ken ; and  the  opinion  now  most  generally 
adopted  is,  that  an  impregnation  of  the  ovum, 
by  the  influence  of  the  male  semen,  is  essential 
to  conception.*  That  the  ovum  is  to  be  im- 
pregnated, there  can  be  no  doubt ; but  as  the 
manner  in  which  such  an  impregnation  is  sup- 
posed to  take  place,  and  the  means  by  which  the 
ovum  afterwards  gets  into  the  Fallopian  tube, 
and  from  thence  into  the  uterus,  are  still  found- 
ed chiefly  on  hypothesis,  we  will  not  attempt 
to  extend  farther  the  investigation  of  a sub- 
ject concerning  which  so  little  can  be  advanc- 
ed with  certainty. 

* The  learned  Abbe  Spallanzani  has  thrown  much  light  on 
this  curious  subject,  and  has  proved  by  a variety  of  experiments, 
that  the  animalcule  exists  entire  in  the  female  ovum  and  that  the 
male  seed  is  only  necessary  to  vivify  and  put  it  in  motion. — His 
experiments  and  observations  are  worthy  the  attentive  perusal  of 
every  physiologist. 


Of  the  Abdomen. 


304 


$.  4.  Of  the  Fcetus  in  Utero. 

Opportunities  of  dissecting  the  human 
gravid  uterus  occurring  but  seldom,  the  state 
of  the  embryo*  immediately  after  conception 
cannot  be  perfectly  known. 

When  the  ovum  descends  into  the  uterus, 
it  is  supposed  to  be  very  minute  ; and  it  is  not 
till  a considerable  time  after  conception  that  the 
rudiments  of  the  embryo  begin  to  be  ascertain- 
ed. 

About  the  third  or  fourth  week  the  eye  may 
discover  the  first  lineaments  of  the  fcetus  ; but 
these  lineaments  are  as  yet  very  imperfect, 
it  being  only  about  the  size  of  a house-fly. 
Two  little  vessels  appear  in  an  almost  transpa- 
rent jelly ; the  largest  of  which  is  destined  to 
become  the  head  of  the  fcetus,  and  the  other 
smaller  one  is  reserved  for  the  trunk.  But  at 
this  period  no  extremities  are  to  be  seen ; the 
umbilical  cord  appears  only  as  a very  minute 
thread,  and  the  placenta  does  not  as  yet  absorb 
the  red  particles  of  the  blood.  At  six  weeks, 
not  only  the  head  but  the  features  of  the  face 
begin  to  be  developed.  The  nose  appears  like 
a small  prominent  line,  and  we  are  able  to  dis- 
cover another  line  under  it,  which  is  destined 
for  the  separation  of  the  lips.  Two  black 
points  appear  in  the  place  of  eyes,  and  two 
minute  holes  mark  the  ears.  At  the  sides  of 

♦-The  rudiments  of  the  child  are  usually  distinguished  by  this 
name  till  the  human  figure  can  be  distinctly  ascertained,  and  then 
it  has  the  appellation  of  fcetus. 


305 


Of  the  Abdomen. 

the  trunk,  both  above  and  below,  we  see  four 
minute  protuberances,  which  are  the  rudiments 
of  the  arms  and  legs.  At  the  end  of  eight 
weeks  the  body  of  the  fcetus  is  upwards  of  an 
inch  in  length,  and  both  the  hands  and  feet  are 
to  be  distinguished.  The  upper  extremities 
are  found  to  increase  faster  than  the  lower  ones, 
and  the  separation  of  the  fingers  is  accomplish- 
ed sooner  than  that  of  the  toes. 

At  this  period  the  human  form  may  be  de- 
cisively ascertained  ; — all  the  parts  of  the  face 
may  be  distinguished,  the  shape  of  the  body 
is  clearly  marked  out,  the  haunches  and  the 
abdomen  are  elevated,  the  fingers  and  toes  are 
separated  from  each  other,  and  the  intestines 
appear  like  minute  threads. 

At  the  end  of  the  third  month,  the  fcetus 
measures  about  three  inches  ; at  the  end  of  the 
fourth  month,  five  inches  ; in  the  fifth  month, 
six  or  seven  inches  ; in  the  sixth  month,  eight 
or  nine  inches  ; in  the  seventh  month,  eleven  or 
twelve  inches ; in  the  eighth  month,  fourteen 
or  fifteen  inches  ; and  at  the  end  of  the  ninth 
month,  or  full  time,  from  eighteen  to  twenty- 
two  inches.  But  as  we  have  not  an  opportu- 
nity of  examining  the  same  fcetus  at  different 
periods  of  pregnancy,  and  as  their  size  and 
length  may  be  influenced  by  the  constitution 
and  mode  of  life  of  the  mother,  calculations  of 
this  kind  must  be  very  uncertain. 

The  fcetus  during  all  this  time  assumes  an 
oval  figure,  which  corresponds  with  the  shape 
of  the  uterus.  Its  chin  is  found  reclining  on 
its  breast  with  its  knees  drawn  up  towards  its 
chin,  and  its  arms  folded  over  them.  But  it 

Q q 


306 


Of  the  Abdomen. 


seems  likely,  that  the  posture  of  some  of  these 
parts  is  varied  in  the  latter  months  of  pregnan- 
cy, so  as  to  cause  those  painful  twitches  which 
its  mother  usually  feels  from  time  to  time.  In 
natural  cases,  its  head  is  probably  placed  to- 
wards the  os  tineas  from  the  time  of  conception 
to  that  of  its  birth  ; though  formerly  it  was  con- 
sidered as  being  placed  towards  the  fundus  ute- 
ri till  about  the  eighth  or  ninth  month,  when 
the  head,  by  becoming  specifically  heavier 
than  the  other  parts  of  the  body,  was  supposed 
to  be  turned  downwards. 

The  capacity  of  the  uterus  increases  in  pro- 
portion to  the  growth  of  the  foetus,  but  with- 
out becoming  thinner  in  its  substance,  as  might 
naturally  be  expected.  The  nourishment  of 
the  foetus,  during  all  this  time,  seems  to  be  de- 
rived from  the  placenta,  which  appears  to  be 
originally  formed  by  that  part  of  the  ovum 
which  is  next  the  fundus  uteri.  The  remain- 
ing part  of  the  ovum  is  covered  by  a mem- 
brane called  spongy  chorion  ;*  within  which  is 
another  called  true  chorion , which  includes  a 
third  termed  amnios  :f  this  contains  a watery 

* Dr.  Hunter  has  described  this  as  a lamella  from  the  inne* 
surface  of  the  uterus.  In  the  latter  months  of  pregnancy  it  be- 
comes gradually  thinner  and  more  connected  with  the  chorion  r 
he  has  named  it  membrana  caduca,  or  decidua , as  it  is  cast  off  with 
the  placenta.  Signior  Scarpa,  with  more  probability,  considers 
it  as  being  composed  of  an  inspissated  coagulable  lymph. 

■f  In  some  quadrupeds,  the  urine  appears  to  be  conveyed  from 
the  bladder  through  a canal  called  urachus  to  the  allantois,  which 
is  a reservoir,  resembling  a long  and  blind  gut,  situated  between 
the  chorion  and  amnios.  The  human  foetus  seems  to  have  no 
such  reservoir,  though  fome  writers  have  supposed  that  it  does 
exist.  From  the  top  of  the  bladder  a few  longitudinal  fibres  are 
extended  to  the  umbilical  chord  ; and  these  fibres  have  been  con- 
sidered as  the  urachus,  though  without  having  been  ever  found 
pervious. 


30.7 


Of  the  Abdomen. 

fluid  which  is  the  liquor  amniif  in  which  the 
foetus  floats  till  the  time  of  its  birth.  On  the 
side  next  the  foetus,  the  placenta  is  covered  by 
the  amnios  and  true  chorion.;  on  the  side  next 
the  mother  it  has  a production  continued  from 
the  spongy  chorion.  The  amnios  and  chorion 
are  remarkably  thin  and  transparent,  having 
no  blood-vessels  entering  into  their  composi- 
tion. The  spongy  chorion  is  opake  and  vas- 
cular. 

In  the  first  months  of  pregnancy,  the  involu- 
cra  bear  a large  proportion  to  their  contents  ; 
but  this  proportion  is  afterwards  reversed,  as 
the  foetus  increases  in  bulk. 

The  placenta,  which  is  the  medium  through 
which  the  blood  is  conveyed  from  the  mother 
to  the  foetus,  and  the  manner  in  which  this 
conveyance  takes  place,  deserve  next  to  be 
considered. 

The  placenta  is  a broad,  flat,  and  spongy 
substance,  like  a cake,  closely  adhering  to  the 
inner  surface  of  the  womb,  usually  near  the 
fundus,  and  appearing  to  be  chiefly  made  up 
of  the  ramifications  of  the  umbilical  arteries 
and  vein,  and  partly  of  the  extremities  of  the 
uterine  vessels.  The  arteries  of  the  uterus 
discharge  their  contents  into  the  substance  of 

* The  liquor  arnnli  coagulates  like  the  lymph.  It  has  been 
supposed  to  pass  into  the  oesophagus,  and  to  afford  nourishment 
to  the  foetus ; but  this  does  not  feem  probable.  Children  have 
come  into  the  world  without  an  oesophagus,  or  any  communica- 
tion between  the  stomach  and  the  mouth  ; but  there  has  been  no 
well  attested  instance  of  a child’s  having  been  born  without  a pla- 
centa ; and  it  does  not  seem  likely,  that  any  of  the  fluid  can  be 
absorbed  through  the  pares  of  the  skin,  the  skin  in  the  foetus  be- 
ing every  where  covered  with  a great  quantity  of  mucus. 


308 


Of  the  Abdomen. 


this  cake  ; and  the  veins  of  the  placenta,  re- 
ceiving the  blood  either  by  a direct  communi- 
cation of  vessels,  or  by  absorption,  at  length 
form  the  umbilical  vein,  which  passes  on  to 
the  sinus  of  the  vena  portse,  and  from  thence 
to  the  vena  cava,  by  means  of  the  canalis  veno- 
sus,  a communication  that  is  closed  in  the 
adult.  But  the  circulation  of  the  blood  through 
the  heart  is  not  conducted  in  the  foetus  as  in 
the  adult : in  the  latter,  the  blood  is  carried 
from  the  right  auricle  of  the  heart  through  the 
pulmonary  artery,  and  is  returned  to  the  left 
auricle  by  the  pulmonary  vein  ; but  a dilatation 
of  the  lungs  is  essential  to  the  passage  of  the 
blood  through  the  pulmonary  vessels,  and  this 
dilatation  cannot  take  place  till  after  the  child  is 
born  and  has  respired.  This  deficiency,  how- 
ever, is  supplied  in  the  foetus  by  the  immedi- 
ate communication  between  the  right  and  left 
auricle,  through  an  oval  opening,  in  the  septum 
which  divides  the  two  auricles,  called  foramen 
ovale.  The  blood  is  likewise  transmitted  from 
the  pulmonary  artery  to  the  aorta,  by  means 
of  a duct  called  canalis  arteriosus , which,  like 
the  canalis  venosus,  and  foramen  ovale,  gra- 
dually closes  after  birth. 

The  blood  is  returned  again  from  the  foetus 
through  two  arteries  called  the  umbilical  arte- 
ries, which  arise  from  the  iliacs.  These  two 
vessels  taking  a winding  course  with  the  vein, 
form  with  that,  and  the  membranes  by  which 
they  are  surrounded,  what  is  called  the  um- 
bilical chord.  These  arteries,  after  ramifying 
through  the  substance  of  the  placenta,  dis- 
charge their  blood  into  the  veins  of  the  uterus ; 


PlateXXY 


y3ref  Lilad c 


Of  the  Abdomen.  $09 

in  the  same  manner  as  the  uterine  arteries  dis- 
charged their  blood  into  the  branches  of  the 
umbilical  vein.  So  that  the  blood  is  constant- 
ly passing  in  at  one  side  of  the  placenta  and 
out  at  the  other  ; but  in  what  particular  man- 
ner it  gets  through  the  placenta  is  a point  not 
yet  determined. 


EXPLANATION  of  PLATES  XXV. 
XXVI.  and  XXVII. 


Plate  XXV. 

Eig.  1.  Shows  the  Contents  of  the  Thorax  and 
Abdomen  in  situ. 

1.  Top  of  the  trachea,  or  wind-pipe.  2 2, 
The  internal  jugular  veins.  3 3,  The  subcla- 
vian veins.  4,  The  vena  cava  descendens. 
5,  The  right  auricle  of  the  heart.  6,  The  right 
ventricle.  7,  Part  of  the  left  ventricle.  8,  The 
aorta  descendens.  9,  The  pulmonary  artery. 
10,  The  right  lung,  part  of  which  is  cut  off  to 
show  the  great  blood-vessels.  11,  The  left 
lung  entire.  12  12,  The  anterior  edge  of  the 
diaphragm.  13  13,  The  two  great  lobes  of 
the  liver.  14,  The  ligamentum  rotundum.  15, 
The  gall-bladder.  16,  The  stomach.  17  17, 
The  jejunum  and  ilium.  18,  The  spleen. 


310 


Of  the  Abdomen. 


Fig.  2.  Shows  the  Organs  subservient  of  the 
Chylopoietic  Viscera, — with  those  of  Urine 
and  Generation. 

1 1,  The  under  side  of  the  two  great  lobes 
of  the  liver,  a,  Lobulus  Spigelih  2,  The  li- 
gamentum  rotundum.  3,  The  gall-bladder. 
4,  The  pancreas.  5,  The  spleen.  6 6,  The 
kidneys.  7,  The  aorta  descendens.  8,  Ve- 
na cava  ascendens.  9 9,  The  renal  veins  co- 
vering the  arteries.  10,  A probe  under  the 
spermatic  vessels  and  a bit  of  the  inferior  me- 
senteric artery,  and  over  the  ureters.  11  11, 
The  ureters.  12  12,  The  iliac  arteries  and 
veins.  13,  The  rectum  intestinum.  14,  The 
bladder  of  urine. 

Fig.  3.  Shows  the  Chylopoietic  Viscera,  and 
Organs  subservient  to  them,  taken  out  of 
the  Body  entire. 

A A,  The  under  side  of  the  two  great  lobes 
of  the  liver.  B,  Ligamentum  rotundum.  C, 
The  gall-bladder.  D,  Ductus  cysticus.  E, 
Ductus  hepaticus.  F,  Ductus  communis  cho- 
ledochus.  G,  Venaportarum.  H,  Arteria  hep- 
atica.  I I,  The  stomach.  K K,  Venae  and  arte- 
riae  gastro-epiploicae,  dextrae  & sinistrae.  L L, 
Venae  & arterite  coronariae  ventriculi.  M,  The 
spleen.  N N,  Mesocolon,  with  its  vessels. 
O O O,  Intestinum  colon.  P,  One  of  the  li- 
gaments of  the  colon,  which  is  a bundle  of 
longitudinal  muscular  fibres.  Q,Q,QQ,,  Jeju- 


511 


Of  the  Abdomen. 

num  and  ilium.  R R,  Sigmoid  flexure  of  the 
colon  with  the  ligament  continued,  and  over  S, 
The  rectum  intestinum.  T T,  Levatores  ani. 
U,  Sphincter  ani.  V,  The  place  to  which  the 
prostate  gland  is  connected.  W,  The  anus. 

Fig.  4.  Shows  the  Heart  of  a Foetus  at  the 
full  time,  with  the  Right  Auricle  cut  open 
to  show  the  Foramen  Ovale,  or  passage  be- 
tween both  Auricles. 

a,  The  right  ventricle.  b,  The  left  ventri- 
cle. c c,  The  outer  side  of  the  right  auricle 
stretched  out.  d d,  The  posterior  side,  which 
forms  the  anterior  side  of  the  septum,  e,  The 
foramen  ovale,  with  the  membrane  or  valve 
which  covers  the  left  side,  f,  Vena  cava  in- 
ferior passing  through  g,  A portion  of  the  dia- 
phragm. 

Fig.  5.  Shows  the  Heart  and  Large  Vessels 
of  a Foetus  at  the  full  time. 

a,  The  left  ventricle,  b,  The  right  ventri- 
cle. c,  A part  of  the  right  auricle.  d,  Left 
auricle,  e e,  The  right  branch  of  the  pulmo- 
nary artery,  f,  Arteria  puimonalis.  g g,  The 
left  branch  of  the  pulmonary  artery,  with  a 
number  of  its  largest  branches  dissected  from 
the  lungs,  h,  The  canalis  arteriosus,  i,  The 
arch  of  the  aorta,  kk,  The  aorta  descendens. 
1,  The  left  subclavian  artery,  m,  The  left  ca- 
rotid artery,  n,  The  right  carotid  artery,  o, 
The  right  subclavian  artery,  p,  The  origin 


312 


Of  the  Abdomen . 


of  the  right  carotid  and  right  subclavian  arteries 
in  one  common  trunk.  q,  The  vena  cava  su- 
perior or  descendens.  r,  The  right  common 
subclavian  vein.  s,  The  left  common  sub- 
clavian vein. 

N.  B.  All  the  parts  described  in  this  figure 
are  to  be  found  in  the  adult,  except  the  cana- 
lis  arteriosus. 


Plate  XXVI. 

Fig.  1.  Exhibits  the  more  superficial  Lympha- 
tic Vessels  of  the  Lower  Extremity. 

A,  The  spine  of  the  os  ilium.  B,  The  os 
pubis.  C,  The  iliac  artery.  D,  The  knee. 
E,  E,  F,  Branches  of  the  crural  artery.  G, 
The  musculus  gastrocnemius.  H,  The  tibia. 
I,  The  tendon  of  the  musculus  tibialis  anticus. 
On  the  out-lines,  a,  A lymphatic  vessel  be- 
longing to  the  top  of  the  foot,  b,  Its  first  di- 
vision into  branches.  c,  c,  c,  Other  divisions 
of  the  same  lymphatic  vessel.  d,  A small 
lymphatic  gland.  e,  The  lymphatic  vessels 
which  lie  between  the  skin  and  the  muscles  of 
the  thigh,  f,  f,  Two  lymphatic  glands  at  the 
upper  part  of  the  thigh  below  the  groin.  g, 
g,  Other  glands.  h,  A lymphatic  vessel 
which  passes  by  the  side  of  those  glands  with- 
out communicating  with  them  ; and,  bending 
towards  the  inside  of  the  groin  at  (i),  opens 
into  the  lymphatic  gland  (k).  1, 1,  Lympha- 

tic glands  in  the  groin,  which  are  common,  to 
the  lymphatic  vessels  of  the  genitals  and  those 


Of  the  Abdomen. 


313 


of  the  lower  extremity.  m,  n,  A plexus  of' 
lymphatic  vessels  passing  on  the  inside  of  the 
iliac  artery. 

Fig.  2.  Exhibits  a Back  View  of  the  lower  Ex- 
tremity, dissected  so  as  to  show  the  deeper- 
seated  Lymphatic  Vessels  which  accompany 
the  Arteries. 

A,  The  os  pubis.  B,  The  tuberosity  of 
the  ischium.  C,  That  part  of  the  os  ilium 
which  was  articulated  with  the  os  sacrum.  D, 
The  extremity  of  the  iliac  artery  appearing 
above  the  groin.  E,  The  knee.  F F,  The 
two  cut  surfaces  of  the  triceps  muscle,  which 
was  divided  to  show  the  lymphatic  vessels  that 
pass  through  its  perforation  along  with  the  cru- 
ral artery.  G,  The  edge  of  the  musculus  gra- 
cilis. H,  The  gastrocnemius  and  soleus,  much 
shrunk  by  being  dried,  and  by  the  soleus  be- 
ing separated  from  the  tibia  to  expose  the  ves- 
sels. I,  The  heel.  K,  The  sole  of  the  foot. 
L,  The  superficial  lymphatic  vessels  passing 
over  the  knee,  to  get  to  the  thigh.  On  the 
out-lines  ; M,  The  posterior  tibial  artery,  a, 
A lymphatic  vessel  accompanying  the  posterior 
tibial  artery,  b,  The  same  vessel  crossing  the 
artery,  c,  A small  lymphatic  gland,  through 
which  this  deep-seated  lymphatic  vessel  passes, 
d,  The  lymphatic  vessel  passing  under  a small 
part  of  the  soleus,  which  is  left  attached  to  the 
bone,  the  rest  being  removed.  e,  The  lym- 
phatic vessel  crossing  the  popliteal  artery,  f, 
g,  h,  Lymphatic  glands  in  the  ham,  through 

R r 


3L4 


Of  the  Abdomen. 


which  the  lymphatic  vessel  passes,  i,  The 
lymphatic  vessel  passing  with  the  crural  ar- 
tery, through  the  perforation  of  the  triceps 
muscle,  k,  The  lymphatic  vessel,  after  it  has 
passed  the  perforation  of  the  triceps,  dividing 
into  branches  which  embrace  the  artery  (1). 
m,  A lymphatic  gland  belonging  to  the  deep- 
seated  lymphatic  vessel.  At  this  place  those 
vessels  pass  to  the  fore  part  of  the  groin,  where 
they  communicate  with  the  superficial  lym- 
phatic vessels,  n,  A part  of  the  superficial 
lymphatic  vessel  appearing  on  the  brim  of  the 
pelvis. 

Fig.  3.  Exhibits  the  Trunk  of  the  Human 

Subject,  prepared  to  show  the  Lymphatic 

Vessels  and  the  Ductus  Thoraeicus. 

A,  The  neck.  B B,  The  two  jugular  veins. 
C,  The  vena  cava  superior.  D D D D,  The 
subclavian  veins.  E,  The  beginning  of  the 
aorta,  pulled  to  the  left  side  by  means  of  a li- 
gature, in  order  to  show  the  thoracic  duct  be- 
hind it.  F,  The  branches  arising  from  the 
curvature  of  the  aorta.  G G,  The  two  caro- 
tid arteries.  H H,  The  first  ribs.  I I,.  The 
trachea.  K K,  The  spine.  L L,  The  vena 
azygos.  M M,  The  descending  aorta.  N, 
Tlie  cceliac  artery,  dividing  into  three  branch- 
es. O,  The  superior  mesenteric  artery.  P, 
The  right  crus  diaphragmatis.  Q.  Q,  The 
two  kidneys.  R,  The  right  emulgent  artery. 
S S,  The  external  iliac  arteries,  g d,  The 
musculi  pso&\  T,  The  internal  iliac  artery. 


315 


Of  the  Abdomen. 

AJ,  The  cavity  of  the  pelvis.  X X,  The  spine 
of  the  os  ilium.  Y Y,  The  groins,  a,  A lym- 
phatic gland  in  the  groin,  into  which  lympha- 
tic vessels  from  the  lower  extremity  are  seen 
to  enter,  b b , The  lymphatic  vessels  of  the 
lower  extremities  passing  under  i Poupart’s  li- 
gament. c c,  A plexus  of  the  lymphatic  ves- 
sels lying  on  each  side  of  the  pelvis,  d , The 
psoas  muscle  with  lymphatic  vessels  lying 
upon  its  inside,  e,  A plexus  of  lymphatics, 
which  having  passed  over  the  brim  of  the  pel- 
vis at  (c),  having  entered  the  cavity  of  the 
pelvis,  and  received  the  lymphatic  vessels  be- 
longing to  the  viscera  contained  in  that  cavity, 
next  ascends,  and  passes  behind  the  iliac  ar- 
tery to  (g).  f Some  lymphatic  vessels  of  the 
left  side  passing  over  the  upper  part  of  the  os 
sacrum,  to  meet  those  of  the  right  side,  g,  The 
right  psoas,  with  a large  plexus  of  lymphatics 
lying  on  its  inside,  h / 1 , The  plexus  lying  on 
each  side  of  the  spine,  i i t,  Spaces  occupied 
by  the  lymphatic  glands,  k,  The  trunk. of  the 
lacteals,  lying  on  the  under  side  of  the  supe- 
rior mesenteric  artery.  The  same  dividing 
into  two  branches,  one  of  which  passes  on 
each  side  of  the  aorta  ; that  of  the  right  side 
being  seen  to  enter  the  thoracic  duct  at  ( m ). 
m,  The  thoracic  duct  beginning  from  the  large 
lymphatics.  «,  The  duct  passing  under  the 
lower  part  of  the  crus  diaphragmatis,  and  un- 
der the  right  emulgent  artery,  o,  The  thora- 
cic duct  penetrating  the  thorax.  j&,  Some  lym- 
phatic vessels  joining  that  duct  in  the  thorax. 

The  thoracic  duct  passing  under  the  curva- 
ture of  the  aorta  to  get  to  the  deft  subclavian 


316 


Of  the  Abdomen. 


vein.  The  aorta  being  drawn  aside  to  show 
the  duct,  r,  A plexus  of  lymphatic  vessels 
passing  upon  the  trachea  from  the  thyroid 
gland  to  the  thoracic  duct. 


Plate  XXVII. 

Fig.  1.  Represents  the  Under  and  Posteriori 
Side  of  the  Bladder  of  Urine,  &c. 

a,  The  bladder,  b b,  The  insertion  of  the 
ureters,  c c,  The  vasa  deferentia,  which  con- 
vey the  semen  from  the  testicles  to  d d,  The 
vesiculae  seminales, — and  pass  through  e,  The 
prostate  gland,  to  discharge  themselves  into 
f,  The  beginning  of  the  urethra. 


Fig.  2.  A transverse  Section  of  the  Penis. 

g g,  Corpora  cavernosa  penis,  h,  Corpus 
cavernosum  urethras,  i,  Urethra,  k,  Septum 
penis.  1 1,  The  septum  between  the  corpus 
cavernosum  urethrae  and  that  of  the  penis. 

Fig.  3.  A longitudinal  Section  of  the  Penis. 

m m,  The  corpora  cavernosa  penis,  divided 
by  o,  The  septum  penis,  n,  The  corpus  ca- 
vernosum glandis,  which  is  the  continuation  of 
that  of  the  urethra. 


\XAXX  W[<\  XTX  ° lli  vx  \ 


Of  the  Abdomen. 


3i7 


Fig.  4.  Represents  the  Female  Organs  of  Ge- 
neration. 

a,  That  side  of  the  uterus  which  is  next  the 
os  sacrum.  1,  Its  fundus.  2,  Its  cervix,  b b, 
The  Fallopian  or  uterine  tubes,  which  open 
into  the  cavity  of  the  uterus  ; — but  the  other 
end  is  open  within  the  pelvis,  and  surrounded 
by  c c,  The  fimbriae.  d d,  The  ovaria.  e,  The 
os  internum  uteri,  or  mouth  of  the  womb, 
f f,  The  ligamenta  rotunda,  which  passes 
without  the  belly,  and  is  fixed  to  the  labia  pu- 
dendi.  g g,  The  cut  edges  of  the  ligamenta 
lata,  which  connects  the  uterus  to  the  pelvis, 
h,  The  inside  of  the  vagina,  i,  The  orifice 
of  the  urethra,  k,  The  clitoris  surrounded  by 
(1,)  The  prseputium.  m m,  The  labia  puden- 
di.  n n,  The  nymphae. 


Fig.  5.  Shews  the  Spermatic  Ducts  of  the 
Testicle  filled  with  Mercury. 

A,  The  vas  deferens.  B,  Its  beginning, 
which  forms  the  posterior  part  of  the  epididy- 
mis. B,  The  middle  of  the  epididymis,  com- 
posed of  serpentine  ducts.  D,  The  head  or 
anterior  part  of  the  epididymis  unravelled, 
e e e e,  The  whole  ducts  which  compose  the 
head  of  the  epididymis  unravelled,  f f,  The 
vasa  deferentia.  g g,  Rete  testis,  h h,  Some 
rectilineal  ducts  which  send  off  the  vasa  defe- 
rentia. i i,  The  substance  of  the  testicle. 


318 


Of  the  Thorax. 


Fig.  6.  The  right  Testicle  entire,  and  the 
Epididymis  filled  with  Mercury. 

A,  The  beginning  of  the  vas  deferens.  B, 
The  vas  deferens  ascending  towards  the 
abdomen.  C,  The  posterior  part  of  the  epididy- 
mis, named  globus  minor.  D,  The  sperma- 
tic vessels  inclosed  in  cellular  substance.  E, 
The  body  of  the  epididymis.  F,  Its  head, 
named  globus  major.  G,  Its  beginning  from 
the  testicle.  H,  The  body  of  the  testicle, 
inclosed  in  the  tunica  albuginea. 


PART  IV.  OF  THE  THORAX. 

HE  thorax,  or  chest,  is  that  cavity  of 


the  trunk  which  extends  from  the  clavi- 
cles, or  the  lower  part  of  the  neck,  to  the  dia- 
phragm, and  includes  the  vital  organs,  which  are 
the  heart  and  lungs  ; and  likewise  the  trachea 
and  oesophagus. — This  cavity  is  formed  by  the 
ribs  and  vertebrae  of  the  back,  covered  by  a 
great  number  of  muscles,  and  by  the  common 
integuments,  and  anteriorly  by  two  glandular 
bodies  called  the  breasts.  The  spaces  between 
the  ribs  are  filled  up  by  muscular  fibres,  which 
from  their  situation  are  called  intercostal  mus- 


cles. 


Of  the  Thorax. 


31& 


Sect.  I.  Of  the  Breasts. 

The  breasts  may  be  defined  to  be  two  large 
conglomerate  glands,  mixed  with  a good  deal  of 
adipose  membrane.  The  glandular  part  is  com- 
posed of  an  infinite  number  of  minute  arteries, 
veins,  and  nerves, 

The  arteries  are  derived  from  two  different 
trunks;  one  of  which  is  called  the  internal , and 
the  other  the  external , mammary  artery.  The 
first  of  these  arises  from  the  subclavian,  and  the 
latter  from  the  axillary. 

The  veins  every  where  accompany  the  arteries 
and  are  distinguished  by  the  same  name.  The 
nerves  are  chiefly  from  the  vertebral  pairs.  Like 
all  other  conglomerate  glands,  the  breasts  are 
made  up  of  a great  many  small  distinct  glands, 
in  which  the  milk  is  secreted  from  the  ultimate 
branches  of  arteries.  The  excretory  ducts  of 
these  several  glands  gradually  uniting  as  they 
approach  the  nipple,  form  the  tubuli  lactiferi, 
which  are  usually  more  than  a dozen  in  num- 
ber, and  open  at  its  apex,  but  have  little  or  no 
communication,  as  has  been  supposed,  at  the 
root  of  the  nipple.  These  ducts,  in  their  course 
from  the  glands,  are  surrounded  by  a ligamen- 
tary elastic  substance,  which  terminates  with 
them  in  the  nipple.  Both  this  substance,  and 
the  ducts  which  it  contains,  are  capable  of  consi- 
derable extension  and  contraction  ; but  in  their 
natural  state  are  moderately  corrugated,  so  as  to 
prevent  an  involuntary  flow  of  milk,  unless  the 
distending  force  be  very  great  from  the  accu- 
mulation of  too  great  a quantity. 


320 


Of  the  Thorax. 

The  whole  substance  of  the  nipple  is  very 
spongy  and  elastic  : its  external  surface  is  un- 
even, and  full  of  small  tubercles.  The  nipple 
is  surrounded  with  a disk  or  circle  of  a different 
colour,  called  the  areola ; and  on  the  inside  of 
the  skin,  under  the  areola,  are  many  sebaceous 
glands,  which  pour  out  a mucus  to  defend  the 
areola  and  nipple : for  the  skin  upon  these 
parts  is  very  thin  ; and  the  nervous  papillae  lying 
very  bare,  are  much  exposed  to  irritation. 

The  breasts  are  formed  for  the  secretion  of 
milk,  which  is  destined  for  the  nourishment  of 
the  child  for  some  time  after  its  birth.  This 
secretion  begins  to  take  place  soon  after  de- 
livery, and  continues  to  flow  for  many  months 
in  very  large  quantities,  if  the  woman  suckles 
her  child. 

The  operation  of  suction  depends  on  the 
principles  of  the  air-pump,  and  the  flow  of 
milk  through  the  lactiferous  tubes  is  facilitated 
by  their  being  stretched  out. 

The  milk,  examined  chemically,  appears  to 
be  composed  of  oil,  mucilage,  and  water,  and  of 
a considerable  quantity  of  sugar.  The  gene- 
rality of  physiologists  have  supposed  that,  like 
the  chyle,  it  frequently  retains  the  properties 
of  the  aliment  and  medicines  taken  into  the 
stomach  ; but  from  some  late  experiments,*  this 
supposition  appears  to  be  ill-founded. 

Sect.  II.  Of  the  Pleura. 

The  cavity  of  the  thorax  is  everywhere  lined 
by  a membrane  of  a firm  texture  called  pleura. 
It  is  composed  of  two  distinct  portions  or  bags, 

* Journ.  de  Med.  1781. 


Of  the  Thorax. 


321 


which,  by  being  applied  to  each  other  laterally, 
form  a septum  called  mediastinum  ; which  di- 
vides the  cavity  into  two  parts,  and  is  attached 
posteriorly  to  the  vertebras  of  the  back,  and 
anteriorly  to  the  sternum.  But  the  two  laminae 
of  which  this  septum  is  formed,  do  not  every 
where  adhere  to  each  other ; for  at  the  lower 
part  of  the  thorax  they  are  separated,  to  afford 
a lodgment  to  the  heart ; and  at  the  upper  part 
of  the  cavity,  they  receive  between  them  the 
thymus. 

The  pleura  is  plentifully  supplied  with 
arteries  and  veins  from  the  internal  mammary 
and  the  intercostals.  Its  nerves,  which  are 
very  inconsiderable,  are  derived  chiefly  from 
the  dorsal  and  intercostal  nerves. 

The  surface  of  the  pleura,  like  that  of  the  pe- 
ritonaeum and  other  membranes  lining  cavities, 
is  constantly  bedewed  with  a serous  moisture* 
which  prevents  adhesion  of  the  viscera. 

The  mediastinum,  by  dividing  the  breast  into 
two  cavities,  obviates  many  inconveniences,  to 
which  we  should  otherwise  be  liable.  It  pre- 
vents the  two  lobes  of  the  lungs  from  com- 
pressing each  other  when  we  lie  on  one  side ; 
and  consequently  contributes  to  the  freedom  of 
respiration,  which  is  disturbed  by  the  least 
pressure  on  the  lungs.  If  the  point  of  a sword 
penetrates  between  the  ribs  into  the  cavity  of 
the  thorax,  the  lungs  on  that  side  cease  to  per- 
form their  office  ; because  the  air  being  ad- 

S s 

* When  this  fluid  is  exhaled  in  too  great  a quantity,  or  is 
not  properly  carried  off,  it  accumulates  and  constitutes  the  hy- 
drops pectoris. 


322 


Of  the  Thorax . 

mitted  through  the  wound,  prevents  the  dila- 
tation of  that  lobe  ; while  the  other  lobe,  which 
is  separated  from  it  by  the  mediastinum,  remains 
unhurt,  and  continues  to  perform  its  function 
as  usual. 

Sect.  II.  Of  the  Thymus. 

The  thymus  is  a glandular  substance,  the 
use  of  which  is  not  perfectly  ascertained,  its 
excretory  duct  not  having  yet  been  discovered. 
It  is  of  an  oblong  figure,  and  is  larger  in  the 
foetus  and  in  young  children  than  in  adults, 
being  sometimes  nearly  effaced  in  very  old 
subjects.  It  is  placed  in  the  upper  part  of 
the  thorax,  between  the  two  laminae  of  the 
mediastinum ; but  at  first  is  not  altogether 
contained  within  the  cavity  of  the  chest,  being 
found  to  border  upon  the  upper  extremity  of  the 
sternum. 

Sect.  IV.  Of  the  Diaphragm . 

The  cavity  of  the  thorax  is  separated  from 
that  of  the  abdomen,  by  a fleshy  and  mem- 
branous substance  called  the  diaphragm  or 
midriff.  The  greatest  part  of  it  is  composed 
of  muscular  fibres;  and  on  this  account  sys- 
tematic writers  usually  place  it  very  properly 
among  the  muscles.  Its  middle  part  is  tendi- 
nous, and  it  is  covered  by  the  pleura  above, 
and  by  the  peritonaeum  below.  It  seems  to 
have  been  improperly  named  septum  transver- 
sum , as  it  does  not  make  a plane  transverse  di- 


323 


Of  the 


Thorax. 


vision  of  the  two  cavities,  but  forms  a kind  of 
vault,  the  fore-part  of  which  is  attached  to  the 
sternum.  Laterally  it  is  fixed  to  the  last  of 
the  true  ribs,  and  to  all  the  false  ribs  5 and  its 
lower  and  posterior  part  is  attached  to  the 
vertebrae  lumborum,  where  it  may  be  said  to 
be  divided  into  two  portions  or  crura.* 

The  principal  arteries  of  the  diaphragm  are 
derived  from  the  aorta,  and  its  veins  pass  into 
the  vena  cava.  Its  nerves  are  chiefly  derived 
from  the  cervical  pairs.  It  affords  a passage 
to  the  vena  cava  through  its  tendinous  part, 
and  to  the  oesophagus  through  its  fleshy  portion. 
The  aorta  passes  down  behind  it  between  its 
crura. 


The  diaphragm  not  only  serves  to  divide 
the  thorax  from  the  abdomen,  but  by  its  mus- 
cular structure  is  rendered  one  of  the  chief 
agents  in  respiration.  When  its  fibres  con- 
tract, its  convex  side,  which  is  turned  towards 
the  thorax,  becomes  gradually  flat,  and  by  in- 
creasing the  cavity  of  the  breast,  affords  room 
for  a complete  dilatation  of  the  lungs,  by  means 
of  the  air  which  is  then  drawn  into  them 
by  the  act  of  inspiration.  The  fibres  of  the  di- 
aphragm then  relax ; and  as  it  resumes  its  for- 
mer state,  the  cavity  of  the  thorax  becomes  gra- 
dually diminished,  and  the  air  is  driven  out 
again  from  the  lungs  by  a motion  contrary  to  the 
former  one,  called  exspiration. 


* Anatomical  writers  have  usually  described  the  diaphragm 
as  being  made  up  of  two  muscles  united  by  a middle  tendon  ; 
and  these  two  portions  or  crura  form  what  they  speak  of  as  the 
inferior  muscle , arising  from  the  sides  and  fore-part  of  the 
vertebrae. 


324 


Of  the  Thorax. 


It  is  in  some  measure,  by  means  of  the  dia- 
phragm, that  we  void  the  faeces  at  the  anus,  and 
empty  the  urinary  bladder..  Besides  these  offi- 
ces, the  acts  of  coughing,  sneezing,  speaking, 
laughing,  gaping,  and  sighing,  coula  not  take 
place  without  its  assistance  ; and  the  gentle 
pressure  which  all  the  abdominal  viscera  re- 
ceive from  its  constant  and  regular  motion,  can- 
not fail  to  assist  in  the  performance  of  the  se- 
veral functions  which  were  ascribed  to  those 
viscera. 


Sect.  V.  Of  the  Trachea. 

The  trachea  or  windpipe,  is  a cartilaginous 
and  membranous  canal,  through  which  the 
air  passes  into  the  lungs.  Its  upper  part,  which 
is  called  the  larynx , is  composed  of  five 
cartilages.  The  uppermost  of  these  cartilages 
is  placed  over  the  glottis  or  mouth  of  the 
larynx,  and  is  called  epiglottis , which  has  been 
before  spoken  of,  as  closing  the  passage  to  the 
lungs  in  the  act  of  swallowing.  At  the  sides 
of  the  glottis  are  placed  the  two  arytenoide 
cartilages,  which  are  of  a very  complex  figure, 
not  easy  to  be  described.  The  anterior  and 
larger  part  of  the  larynx  is  made  up  of  two 
cartilages  ; one  of  which  is  called  thyroides  or 
scutiformis , from  its  being  shaped  like  a buck- 
ler ; and  the  other  cricoides  or  annularis , from 
its  resembling  a ring.  Both  these  cartilages 
may  be  felt  immediately  under  the  skin,  at  the 
fore-part  of  the  throat,  and  the  thyroides,  by 
its  convexity,  forms  an  eminence  called  po- 


325 


Of  the  Thorax. 

mum  adami , which  is  usually  more  considerable 
in  the  male  than  in  the  female  subject. 

All  these  cartilages  are  united  to  each  other 
by  means  of  very  elastic,  ligamentous  fibres ; 
and  are  enabled  by  the  as  sistance  of  their  several 
muscles,  to  dilate  or  contract  the  passage  of 
the  larynx,  and  to  perform  that  variety  of 
motion  which  seems  to  point  out  the  larynx  as 
the  principal  organ  of  the  voice  ; for  when 
the  air  passes  out  through  a wound  in  the 
trachea,  it  produces  no  sound. 

These  cartilages  are  moistened  by  a mucus 
which  seems  to  be  secreted  by  minute  glands 
situated  near  them.  The  upper  part  of  the 
trachea  is  covered  anteriorly  and  laterally  by  a 
considerable  body,  which  is  supposed  to  be  of 
a glandular  structure,  and  from  its  situation 
near  the  thyroid  cartilage  is  called  the  thyroid 
gland ; though  its  excretory  duct  has  not  yet 
been  discovered,  or  its  use  ascertained. 

The  glottis  is  interiorly  covered  by  a very 
fine  membrane,  which  is  moistened  by  a 
constant  supply  of  a watery  fluid.  From  the 
larynx  the  canal  begins  to  take  the  name  of 
trachea  or  aspera  arteria , and  extends  from 
thence  as  far  down  as  the  third  or  fourth  verte- 
bra of  the  back,  where  it  divides  into  two 
branches  which  are  the  right  and  left  brom 
chial  tube.  Each  of  these  bronchi*  ramifies 

* The  right  bronchial  tube  is  usually  found  to  be  somewhat 
shorter  and  thicker  than  the  left  ; and  M.  Portal,  who  has 
published  a memoir  on  the  action  of  the  lungs  on  the  aorta  in 
respiration,  obferves  that  the  left  bronchial  tube  is  closely 
connected  by  the  aorta ; and  from  some  experiments  he  is 
induced  to  conclude,  that  in  the  first  respirations  the  air  only 
enters  into  the  right  lobe  of  the  lungs.  Mcmoires  de  V Academic 
Roy  ale  des  Sciences,  1769. 


326 


Of  the  Thorax. 


through  the  substance  of  that  lobe  of  the  lungs 
to  which  it  is  distributed,  by  an  infinite 
number  of  branches,  which  are  formed  of  car- 
tilages separated  from  each  other  like  those  of 
the  trachea,  by  an  intervening  membranous  and 
ligamentary  substance.  Each  of  these  cartilages 
is  of  an  angular  figure ; and  as  they  become 
gradually  less  and  less  in  their  diameter,  the 
lower  ones  are  in  some  measure  received  into 
those  above  them,  when  the  lungs,  after  being 
inflated,  gradually  collapse  by  the  air  being 
pushed  out  from  them  in  exspiration.  As  the 
branches  of  the  bronchi  become  more  minute, 
their  cartilages  become  more  and  more  angular 
and  membranous,  till  at  length  they  are  found 
to  be  perfectly  membranous,  and  at  last  become 
invisible. 

The  trachea  is  furnished  with  fleshy  or 
muscular  fibres  ; some  of  which  pass  through 
its  whole  extent  longitudinally,  while  the  others 
are  carried  round  it  in  a circular  direction ; so 
that  by  the  contraction  or  relaxation  of  these 
fibres,  it  is  enabled  to  shorten  or  lengthen  itself, 
and  likewise  to  dilate  or  contract  the  diameter 
of  its  passage. 

The  trachea  and  its  branches,  in  all  their 
ramifications,  are  furnished  with  a great  num- 
ber of  small  glands  which  are  lodged  in  their 
cellular  substance,  and  discharge  a mucous  fluid 
on  the  inner  surface  of  these  tubes. 

The  cartilages  of  the  trachea,  by  keeping  it 
constantly  open,  afford  a free  passage  to  the  air 
which  we  are  obliged  to  be  incessantly  respir- 
ing ; and  its  membranous  part,  by  being  capable 


327 


Of  the  Thorax. 

of  contraction  and  dilatation,  enables  us  to  re- 
ceive and  expel  the  air  in  a greater  or  less  quan- 
tity, and  with  more  or  less  velocity,  as  may  be 
required  in  singing  or  in  declamation.  '1  his 
membranous  structure  of  the  trachea  poste- 
riorly, seems  likewise  to  assist  in  the  descent 
of  the  food,  by  preventing  that  impediment  to 
its  passage  down  the  oesophagus,  which  might 
be  expected  if  the  cartilages  were  complete 
rings. 

The  trachea  receives  its  arteries  from  the 
carotid  and  subclavian  arteries,  and  its  veins 
pass  into  the  jugulars.  Its  nerves  arise  from 
the  recurrent  branch  of  the  eighth  pair,  and 
from  the  cervical  plexus. 

Sect.  VI.  Of  the  Lungs. 

The  lungs  fill  the  greater  part  of  the  cavity 
of  the  breast.  They  are  of  a soft  and  spongy 
texture,  and  are  divided  into  two  lobes,  which 
are  separated  from  each  other  by  the  me- 
diastinum, and  are  externally  covered  by  a 
production  of  the  pleura.  Each  of  these  is 
divided  into  two  or  three  lesser  lobes ; and  we 
commonly  find  three  in  the  right  side  of  the 
cavity,  and  two  in  the  left. 

To  discover  the  structure  of  the  lungs,  it  is 
required  to  follow  the  ramifications  of  the  bron- 
chi, which  were  described  in  the  last  section. 
These  becoming  gradually  more  and  more 
minute,  at  length  terminate  in  the  cellular 
spaces  or  vesicles,  which  make  up  the  greatest 
part  of  the  substance  of  the  lungs,  and  readily 
communicate  with  each  other. 


328 


Of  the  Thorax . 


The  lungs  seem  to  possess  but  little  sensibili- 
ty. Their  nerves,  which  are  small  and  few  in 
number,  are  derived  from  the  intercostal  and 
eighth  pair.  This  last  pair  having  reached 
the  thorax,  sends  off  a branch  on  each  side  of 
the  trachea,  called  the  recurrent , which  reas- 
cends at  the  back  part  of  the  trachea,  to  which 
it  furnishes  branches  in  its  ascent,  as  well  as 
to  tne  oesophagus,  but  it  is  chiefly  distributed  to 
the  larynx  and  its  muscles.  By  dividing  the 
recurrent  and  superior  laryngeal  nerves  at  their 
origin,  an  animal  is  deprived  of  its  voice. 

There  are  two  series  of  arteries  which  carry 
blood  to  the  lungs  : these  are  the  arterias  bron- 
chiales,  and  the  pulmonary  artery. 

The  arterise  bronchiales  begin  usually  by 
two  branches ; one  of  which  commonly  arises 
from  the  right  intercostal,  and  the  other  from 
the  trunk  of  the  aorta : but  sometimes  there 
are  three  of  these  arteries,  and  in  some  sub- 
jects only  one.  The  use  of  these  arteries  is  to 
serve  for  the  nourishment  of  the  lungs,  and 
their  ramifications  are  seen  creeping  every 
where  on  the  branches  of  the  bronchi.  The 
blood  is  brought  back  from  them  by  the  bron- 
chial vein  into  the  vena  azygos. 

The  pulmonary  artery  and  vein  are  not  in- 
tended for  the  nourishment  of  the  lungs ; but 
the  blood  in  its  passage  through  them  is  de- 
stined to  undergo  some  changes,  or  to  acquire 
certain  essential  properties  (from  the  action  of 
the  air),  which  it  has  lost  in  its  circulation 
through  the  other  parts  of  the  body.  The 
pulmonary  artery  receives  the  blood  from  the 
right  ventricle  of  the  heart,  and  dividing  into 


3 29 


Of  the  Thorax . 

two  branches,  accompanies  the  bronchi  every 
where,  by  its  ramifications  through  the  lungs ; 
and  the  blood  is  afterwards  conveyed  back  by 
the  pulmonary  vein,  which  gradually  forming 
a considerable  trunk,  goes  to  empty  itself  into 
the  left  ventricle  of  the  heart ; so  that  the 
quantity  of  blood  which  enters  into  the  lungs, 
is  perhaps  greater  than  that  which  is  sent  in 
the  same  proportion  of  time  through  all  the 
other  parts  of  the  body. 


Sect.  VII.  Of  Respiration. 

J 

Respiration  constitutes  one  of  those  func- 
tions which  are  properly  termed  vital , as  being 
essential  to  life ; for  to  live  and  to  breathe  are 
in  fact  synonymous  terms.  It  consists  in  an 
alternate  contraction  and  dilatation  of  the  tho- 
rax, by  first  inspiring  air  into  the  lungs,  and 
then  expelling  it  from  them  in  exspiration. 

It  will  perhaps  be  easy  to  distinguish  and 
point  out  the  several  phenomena  of  respira- 
tion ; but  to  explain  their  physical  cause  will 
be  attended  with  difficulty,  for  it  will  natural- 
ly be  inquired,  how  the  lungs,  when  emptied 
of  the  air,  and  contracted  by  exspiration,  be- 
come again  inflated,  they  themselves  being 
perfectly  passive  ? How  the  ribs  are  elevated 
in  opposition  to  their  own  natural  situation  ? 
and  why  the  diaphragm  is  contracted  down- 
wards towards  the  abdomen?  Were  we  to  as- 
sert that  the  air,  by  forcing  its  way  into  the 
cavity  of  the  lungs,  dilated  them,  and  conse- 
quently elevated  the  ribs,  and  pressed  down 

T t 


330  Of  the  Thorax. 

the  diaphragm,  we  should  speak  erroneously. 
What  induces  the  first  inspiration,  it  is  not 
easy  to  ascertain  ; but  after  an  animal  has  once 
respired,  it  would  seem  likely  that  the  blood, 
after  exspiration,  finding  its  passage  through 
the  lungs  obstructed,  becomes  a stimulus, 
which  induces  the  intercostal  muscles  and  the 
diaphragm  to  contract,  and  enlarge  the  cavity 
of  the  thorax,  in  consequence  perhaps  of  a 
certain  nervous  influence,  which  we  will  not 
here  attempt  to  explain.  The  air  then  rushes 
into  the  lungs  ; every  branch  of  the  bronchial 
tubes,  and  all  the  cellular  spaces  into  which 
they  open,  become  fully  dilated ; and  the  pul- 
monary vessels  being  equally  distended,  the 
blood  flows  through  them  with  ease.  But  as 
the  stimulus  which  first  occasioned  this  dilata- 
tion ceases  to  operate,  the  muscles  gradually 
contract,  the  diaphragm  rises  upwards  again, 
and  diminishes  the  cavity  of  the  chest ; the 
ribs  return  to  their  former  state  ; and  as  the 
air  passes  out  in  exspiration,  the  lungs  gradu- 
ally collapse,  and  a resistance  to  the  passage 
of  the  blood  again  takes  place.  But  the  heart 
continuing  to  receive  and  expel  the  blood,  the 
pulmonary  artery  begins  again  to  be  distend- 
ed, the  stimulus  is  renewed,  and  the  same 
process  is  repeated,  and  continues  to  be  re- 
peated, in  a regular  succession,  during  life  : 
for  though  the  muscles  of  respiration,  having 
a mixed  motion,  are  (unlike  the  heart)  in  some 
measure  dependent  on  the  will,  yet  no  human 
being,  after  having  once  respired,  can  live 
many  moments  without  it.  In  an  attempt  to 
hold  one’s  breath,  the  blood  soon  begins  to 


Of  the  Thorax . 331 

distend  the  veins,  which  are  unable  to  empty 
their  contents  into  the  heart ; and  we  are  able 
only,  during  a very  little  time,  to  resist  the. 
stimulus  to  inspiration.  In  drowning,  the  cir- 
culation seems  to  be  stopped  upon  this,  prin- 
ciple ; and  in  hanging,  the  pressure  made  on 
the  jugular  veins,  may  co-operate  with,  the 
stoppage  of  respiration  in  bringing  on  death. 

Till  within  these  few  years  physiologists 
were  entirely  ignorant  of  the  use  of  respira- 
tion. It  was  at  length  discovered  in  part  by 
the  illustrious  Dr.  Priestley.  Pie  found  tha.t 
the  air  exspired  by  animals  was  phlogistica- 
ted ; and  that  the  air  was  fitter  for  respiration, 
or  for  supporting  animal  life,  in  proportion  as 
it  was  freer  from  the  phlogistic  principle.  It 
had  long  been  observed,  that  the  blood  in  pas- 
sing through  the  lungs  acquired  a more  florid 
colour.  He  therefore  suspected,  that  it  was 
owing  to  its  having  imparted  phlogiston  to  the 
air:  and  he  satisfied  himself  of  the  truth  of 
this  idea,  by  experiments,  which  showed,  that 
the  crassamentum  of  extravasated  blood,  phlo- 
gisticated  air  in  proportion  as  it  lost  its  dark 
colour.  He  farther  found,  that  blood  thus 
reddened  had  a strong  attraction  for  phlogis- 
ton ; insomuch  that  it  was  capable  of  taking  it 
from  phlogisticated  air,  thereby  becoming  of 
a darker  colour.  From  hence  it  appeared  that 
the  blood,  in  its  circulation  through  the  arte- 
rial system,  imbibes  a considerable  quantity 
of  phlogiston,  which  is  discharged  from  it  to 
the  air  in  the  lungs. 

This  discovery  has  since  been  prosecuted 
by  two  very  ingenious  physiologists,  Dr.  Craw- 


332 


Of  the  Thorax. 

ford  and  Mr.  Elliot.  It  had  been  shown  by 
professors  Black  and  Irvine,  that  different  bo- 
dies have  different  capacities  for  containing 
fire.  For  example,  that  oil  and  water,  when 
equally  hot  to  the  sense  and  the  thermometer, 
contain  different  proportions  of  that  principle  ; 
and  that  unequal  quantities  of  it  are  required, 
in  order  to  raise  those  substances  to  like  tem- 
peratures. The  inquiries  of  Dr.  Crawford 
and  Mr.  Elliot  tend  to  prove,  that  the  capaci- 
ties of  bodies  for  containing  fire  are  diminish- 
ed by  the  addition  of  phlogiston,  and  increas- 
ed by  its  separation  : the  capacity  of  calx  of 
antimony,  for  example,  being  greater  than 
that  of  the  antimony  itself.  Common  air  con- 
tains a great  quantity  of  fire  ; combustible  bo- 
dies very  little.  In  combustion,  a double  elec- 
tive attraction  takes  place  ; the  phlogiston  of 
the  body  being  transferred  to  the  air,  the  fire 
contained  in  the  air  to  the  combustible  body. 
But  as  the  capacity  of  the  latter  is  not  increas- 
ed so  much  as  that  of  the  former  is  diminish- 
ed, only  part  of  the  extricated  fire  will  be  ab- 
sorbed by  the  body.  The  remainder  there- 
fore will  raise  the  temperature  of  the  com- 
pound ; and  hence  we  may  account  for  the  heat 
attending  combustion.  As  the  use  of  respira- 
tion is  to  dephlogisticate  the  blood,  it  seems 
probable,  that  a like  double  elective  attraction 
takes  place  in  this  process  ; the  phlogiston  of 
the  blood  being  transferred  to  the  air,  and  the 
fire  contained  in  the  air  to  the  blood ; but  with 
this  difference,  that  the  capacities  being  equal, 
the  whole  of  the  extricated  fire  is  absorbed  by 
the  latter.  The  blood  in  this  state  circulating 


Of  the  Thorax. 


335 


through  the  body,  imbibes  phlogiston,  and  of 
course  gives  out  its  fire  ; part  only  of  which  is 
absorbed  by  the  parts  furnishing  the  phlogis- 
ton, the  remainder,  as  in  combustion,  becom- 
ing sensible  ; and  is  therefore  the  cause  ol  the 
heat  of  the  body,  or  what  is  called  animal 
heat. 

In  confirmation  of  this  doctrine  it  may  be 
observed,  that  the  venous  blood  contains  less 
fire  than  the  arterial ; combustible  bodies  less 
than  incombustible  ones  ; and  that  air  contains 
less  of  this  principle,  according  as  it  is  render- 
ed, by  combination  with  phlogiston,  less  fit  for 
respiration.* 

In  ascending  very  high  mountains,  respira- 
tion is  found  no  become  short  and  frequent, 
and  sometimes  to  be  attended  with  a spitting 
of  blood.  These  symptoms  seem  to  be  occa- 
sioned by  the  air  being  too  rare  and  thin  to 
dilate  the  lungs  sufficiently ; and  the  blood 
gradually  accumulating  in  the  pulmonary  ves- 
sels, sometimes  bursts  through  their  coats,  and 
is  brought  up  by  coughing.  This  has  likewise 
been  accounted  for  in  a different  way,  by  sup- 
posing that  the  air  contained  in  the  blood,  not 
receiving  an  equal  pressure  from  that  of  the 
atmosphere,  expands,  and  at  length  ruptures 
the  very  minute  branches  of  the  pulmonary 
vessels ; upon  the  same  principle  that  fruits 
and  animals  put  under  the  receiver  of  an  air- 
pump,  are  seen  to  swell  as  the  outer  air  be- 
comes exhausted.  But  Dr.  Darwin  of  Litch- 

* See  Crawford’s  Experiments  and  Observations  on  Animal 
Heat,  and  Elliot’s  Philosophical  Observations. 


334 


Of  the  Thorax. 


field  has  lately  published  some  experiments, 
which  seem  to  prove,  that  no  air  or  elastic 
vapour  does  exist  in  the  blood-vessels,  as  has 
been  generally  supposed  ; and  he  is  induced 
to  impute  the  spitting  of  blood,  which  has 
sometimes  taken  place  in  ascending  high  moun- 
tains, to  accident,  or  to  violent  exertions  ; as 
it  never  happens  to  animals  that  are  put  into 
the  exhausted  receiver  of  an  air-pump,  where 
the  diminution  of  pressure  is  many  times 
greater  than  on  the  summit  of  the  highest 
mountains. 

Sect.  VIII.  Of  the  Voice. 

Respiration  has  already  been  described  as 
affording  us  many  advantages ; and  next  to 
that  of  life,  its  most  important  use  seems  to  be 
that  of  forming  the  voice  and  speech.  The 
ancients,  and  almost  all  the  moderns,  have 
considered  the  organ  of  speech  as  a kind  of 
musical  instrument,  which  may  be  compared 
to  a flute,  to  an  hautboy,  to  an  organ,  &x.  and 
they  argue  after  the  following  manner. 

The  trachea,  which  begins  at  the  root  of 
the  tongue,  and  goes  to  terminate  in  the  lungs, 
may  be  compared  to  the  pipe  of  an  organ,  the 
lungs  dilating  like  bellows  during  the  time  of 
inspiration  ; and  as  the  air  is  driven  out  from 
them  in  exspiration,  it  finds  its  passage  strait- 
ened by  the  cartilages  of  the  larynx,  against 
which  it  strikes.  As  these  cartilages  are  more 
or  less  elastic,  they  occasion  in  their  turn  more 
or  less  vibration  in  the  air,  and  thus  produce 


Of  the  Thorax. 


335 


the  sound  of  the  voice ; the  variation  in  the 
sound  and  tone  of  which  depends  on  the  state 
of  the  glottis,  which,  when  straitened,  pro- 
duces an  acute  tone,  and  a grave  one  when 
dilated. 

The  late  M.  Ferein  communicated  to  the 
French  Academy  of  Sciences  a very  ingenious 
theory  on  the  formation  of  the  voice.  He  con- 
sidered the  organ  of  the  voice  as  a string , as 
well  as  a wind , instrument ; so  that  what  art 
has  hitherto  been  unable  to  construct,  and 
what  both  the  fathers  Mersenne  and  Kircher 
so  much  wished  to  see,  M.  Ferein  imagined 
he  had  at  length  discovered  in  the  human  body. 
He  observes,  that  there  are  at  the  edges  of  the 
glottis  certain  tendinous  chords,  placed  hori- 
zontally across  it,  which  are  capable  of  consi- 
derable vibration,  so  as  to  produce  sound,  in 
the  same  manner  as  it  is  produced  by  the 
strings  of  a violin  or  a harpsichord : and  he 
supposes  that  the  air,  as  it  passes  out  from 
the  lungs,  acts  as  a bow  on  these  strings, 
while  the  efforts  of  the  breast  and  lungs  regu- 
late its  motion,  and  produce  the  variety  of 
tones.  So  that  according  to  this  system  the 
variation  in  the  voice  is  not  occasioned  by  the 
dilatation  or  contraction  of  the  glottis,  but  by 
the  distention  or  relaxation  of  these  strings, 
the  sound  being  more  or  less  acute  in  propor- 
tion as  they  are  more  or  less  stretched  out. 
Another  writer  on  this  subject  supposes,  that 
the  organ  of  voice  is  a double  instrument, 
which  produces  in  unison  two  sounds  of  a dif- 
ferent nature ; one  by  means  of  the  air,  and 
the  other  by  means  of  the  chords  of  the  glot- 


S3  6 


Of  the  Thorax. 


tis.  Neither  of  these  systems,  however,  are 
universally  adopted.  They  are  both  liable  to 
insuperable  difficulties ; so  that  the  manner  in 
which  the  voice  is  formed  has  never  yet  been 
satisfactorily  ascertained : we  may  observe, 
however,  that  the  sound  produced  by  the  glottis 
is  not  articulated.  To  effect  this,  it  is  requir- 
ed to  pass  through  the  mouth,  where  it  is  dif- 
ferently modified  by  the  action  of  the  tongue, 
which  is  either  pushed  against  the  teeth,  or 
upwards  towards  the  palate  ; detaining  it  in  its 
passage,  or  permitting  it  to  flow  freely,  by  con- 
tracting or  dilating  the  mouth. 


Sect.  IX.  Of  Dejection. 

By  dejection  we  mean  the  act  of  voiding  the 
faeces  at  the  anus  5 and  an  account  of  the  man- 
ner in  which  this  is  conducted  was  reserved 
for  this  part  of  the  work,  because  it  seemed 
to  require  a knowledge  of  respiration  to  be 
perfectly  understood. 

The  intestines  were  described  as  having  a 
peristaltic  motion,  by  which  the  feces  were 
gradually  advancing  towards  the  anus.  Now, 
whenever  the  feces  are  accumulated  in  the 
intestinum  rectum  in  a sufficient  quantity  to 
become  troublesome,  either  by  their  weight  or 
acrimony,  they  excite  a certain  uneasiness 
which  induces  us  to  go  to  stool. — To  effect 
this,  we  begin  by  making  a considerable  in- 
spiration ; in  consequence  of  which  the  dia- 
phragm is  carried  dow'nwards  towards  the  low- 
er belly ; the  abdominal  muscles  are  at  the 


Of  the  Thorax. 


337 


same  time  contracted  in  obedience  to  the  will ; 
and  the  intestines  being  compressed  on  all 
sides,  the  resistance  o.f  the  sphincter  is  over- 
come, and  the  feces  pass  out  at  the  anus  ; 
which  is  afterwards  drawn  up  by  its  longitu- 
dinal fibres,  which  are  called  levatores  ani , and 
then  by  means  of  its  sphincter  is  again  con- 
tracted : but  it  sometimes  happens,  as  in  dy- 
senteries for  instance,  that  the  feces  are  very 
liquid,  and  have  considerable  acrimony ; and 
then  the  irritation  they  occasion  is  more  fre- 
quent, so  as  to  promote  their  discharge  with- 
out any  pressure  from  the  diaphragm  or  ab- 
dominal muscles  ; and  sometimes  involuntari- 
ly, as  is  the  case  when  the  sphincter  becomes 
paralytic. 

Sect.  X.  Of  the  Pericardium , and  of  the 
Heart  and  its  Auricles. 

The  two  membranous  bags  of  the  pleura, 
which  were  described  as  forming  the  medias- 
tinum, recede  one  from  the  other,  so  as  to  af- 
ford a lodgment  to  a firm  membranous  sac,  in 
which  the  heart  is  securely  lodged  ; this  sac, 
which  is  the  pericardium , appears  to  be  com- 
posed of  two  tunics,  united  to  each  other  by 
cellular  membrane. — The  outer  coat,  which 
is  thick,  and  in  some  places  of  tendinous  com- 
plexion, is  a production  of  the  mediastinum  ; 
the  inner  coat,  which  is  extremely  thin,  is  re- 
flected over  the  auricles  and  ventricles  of  the 
heart,  in  the  same  manner  as  the  tunica  con- 

11  u 


338  Of  the  Thorax. 

junctiva,  after  lining  the  eye-lids,  is  reflected 
over  the  eye. 

This  bag  adheres  to  the  tendinous  part  of 
the  diaphragm,  and  contains  a coagulable 
lymph,  the  liquor  pericardii , which  serves  to 
lubricate  the  heart  and  facilitate  its  motions  ; 
and  seems  to  be  secreted  and  absorbed  in  the 
same  manner  as  it  is  in  the  other  cavities  of 
the  body. 

The  arteries  of  the  pericardium  are  derived 
from  the  phrenic,  and  its  veins  pass  into  veins 
of  the  same  name ; its  nerves  are  likewise 
branches  of  the  phrenic. 

The  size  of  the  pericardium  is  adapted  to 
that  of  the  heart,  being  usually  large  enough 
to  contain  it  loosely.  As  its  cavity  does  not 
extend  to  the  sternum,  the  lungs  cover  it  in 
inspiration  ; and  as  it  every  where  invests  the 
heart,  it  effectually  secures  it  from  being  in- 
jured by  lymph,  pus,  or  any  other  fluid,  ex- 
travasated  into  the  cavities  of  the  thorax. 

The  heart  is  a hollow  muscle  of  a conical 
shape,  situated  transversely  between  the  two 
laminae  of  the  mediastinum,  at  the  lower  part 
of  the  thorax  ; having  its  basis  turned  towards 
the  right  side,  and  its  point  or  apex  towards 
the  left — Its  lower  surface  is  somewhat  flat- 
tened towards  the  diaphragm.  Its  basis,  from 
which  the  great  vessels  originate,  is  covered 
with  fat,  and  it  has  two  hollow  and  fleshy  ap- 
pendages, called  auricles. — Round  these  seve- 
ral openings,  the  heart  seems  to  be  of  a firm 
ligamentous  texture,  from  which  all  its  fibres 
seem  to  originate  ; and  as  they  advance  from 


339 


Of  the  Thorax. 

thence  towards  the  apex,  the  substance  of  the 
heart  seems  to  become  thinner. 

The  heart  includes  two  cavities  or  ventricles , 
which  are  separated  from  each  other  by  a 
fleshy  septum  ; one  of  these  is  called  the  rights 
and  the  other  the  left , ventricle ; though  per- 
haps, with  respect  to  their  situation,  it  would 
be  more  proper  to  distinguish  them  into  the 
anterior  and  posterior  ventricles. 

The  heart  is  exteriorly  covered  by  a very 
fine  membrane  ; and  its  structure  is  perfectly 
muscular  or  fleshy,  being  composed  of  fibres 
which  are  described  as  passing  in  different  di- 
rections ; some  as  being  extended  longitudi- 
nally from  the  basis  to  the  apex  ; others,  as 
taking  an  oblique  or  spiral  course  ; and  a third 
sort  as  being  placed  in  a transverse  direction.* 
— Within  the  two  ventricles  we  observe  seve- 
ral furrows  ; and  there  are  likewise  tendinous 
strings,  which  arise  from  fleshy  columns  in  the 
two  cavities,  and  are  attached  to  the  valves  of 
the  auricles  : That  the  use  of  these  and  the 
other  valves  of  the  heart  may  be  understood, 
it  must  be  observed,  that  four  large  vessels 
pass  out  from  the  basis  of  the  heart,  viz.  two 
arteries  and  two  veins  : and  that  each  of  these 
vessels  is  furnished  with  a thin  membranous 
production,  which  is  attached  all  round  to  the 
borders  of  their  several  orifices,  from  whence 
hanging  loosely  down  they  appear  to  be  divid- 
ed into  two  or  three  distinct  portions.  But  as 

* Authors  differ  about  the  course  and  distinctions  of  these 
fibres  ; and  it  seems  right  to  observe,  that  the  structure  of  the 
heart  being  more  compact  than  that  of  other  muscles,  its  fibres 
are  not  easily  separated. 


340 


Of  the  Thorax. 


their  uses  in  the  arteries  and  veins  are  differ- 
ent, so  are  they  differently  disposed.  Those 
of  the  arteries  are  intended  to  give  way  to  the 
passage  of  the  blood  into  them  from  the  ven- 
tricles, but  to  oppose  its  return : and,  on  the 
contrary,  the  valves  of  the  veins  are  construct- 
ed so  as  to  allow  the  blood  only  to  pass  into 
the  heart.  In  consequence  of  these  different 
uses,  we  find  the  valves  of  the  pulmonary  ar- 
tery and  of  the  aorta  attached  to  the  orifices 
of  those  vessels,  so  as  to  have  their  concave 
surfaces  turned  towards  the  artery ; and  their 
convex  surfaces,  which  mutually  meet  toge- 
ther, being  placed  towards  the  ventricle,  only 
permit  the  blood  to  pass  one  way,  which  is  into 
the  arteries.  There  are  usually  three  of  these 
valves  belonging  to  the  pulmonary  artery,  and 
as  many  to  the  aorta  ; and  from  their  figure 
they  are  called  valvule  semilunares.  The  com- 
munication between  the  two  great  veins  and 
the  ventricles  is  by  means  of  the  two  appen- 
dages or  auricles  into  which  the  blood  is  dis- 
charged ; so  that  the  other  valves  which  may 
be  said  to  belong  to  the  veins,  are  placed  in 
each  ventricle,  where  the  auricle  opens  into  it. 
The  valves  in  the  right  ventricle  are  usually 
three  in  number,  and  are  named  valvule?  tri- 
cuspides  ; but  in  the  left  ventricle  we  common- 
ly observe  only  two,  and  these  are  the  valvulce 
mitrales.  The  membranes  which  form  these 
valves  in  each  cavity  are  attached  so  as  to  pro- 
ject somewhat  forward ; and  both  the  tricus- 
pides  and  the  mitrales  are  connected  with  the 
tendinous  strings,  which  were  described  as 
arising  from  the  fleshy  column a.  By  the  con- 


541 


Of  the  Thorax. 

traction  of  either  ventricle,  the  blood  is  driv- 
en into  the  artery  which  communicates  with 
that  ventricle ; and  these  tendinous  strings 
being*  gradually  relaxed  as  the  sides  of  the  ca- 
vity are  brought  nearer  to  each  other,  the 
valves  naturally  close  the  opening  into  the  au- 
ricle, and  the  blood  necessarily  directs  its 
course  into  the  then  only  open  passage,  which 
is  into  the  artery ; but  after  this  contraction, 
the  heart  becomes  relaxed,  the  tendinous 
strings  are  again  stretched  out,  and,  drawing 
the  valves  of  the  auricle  downwards,  the  blood 
is  poured  by  the  veins  into  the  ventricle,  from 
whence,  by  another  contraction,  it  is  again 
thrown  into  the  artery,  as  will  be  described 
hereafter.  The  right  ventricle  is  not  quite  so 
long,  though  somewhat  larger,  than  the  left ; 
but  the  latter  has  more  substance  than  the 
other:  and  this  seems  to  be,  because  it  is  in- 
tended to  transmit  the  blood  to  the  most  dis- 
tant parts  of  the  body,  whereas  the  right  ven- 
tricle distributes  it  only  to  the  lungs. 

The  heart  receives  its  nerves  from  the  par 
vagum  and  the  intercostals.  The  arteries 
which  serve  for  its  nourishment  are  two  in 
number,  and  arise  from  the  aorta.  They  sur- 
round in  some  measure  the  basis  of  the  heart, 
and  from  this  course  are  called  the  coronary 
arteries.  From  these  arteries  the  blood  is  re- 
turned by  veins  of  the  same  name  into  the  au- 
ricles, and  even  into  the  ventricles. 

The  muscular  bags  called  the  auricles  are 
situated  at  the  basis  of  the  heart,  at  the  sides 
of  each  other;  and,  corresponding  with  the 
two  ventricles,  are  like  those  two  cavities  dis- 


342 


Of  the  Thorax. 


tinguished  into  right  and  left.  These  sacs, 
which  are  interiorly  unequal,  have  externally 
a jagged  appendix ; which,  from  its  having 
been  compared  to  the  extremity  of  an  ear,  has 
given  them  their  name  of  auricles. 

Sect.  XI.  Angiology , or  a Description  of  the 
Bloocl-vessels. 

The  heart  has  been  described  as  contracting 
itself,  and  throwing  the  blood  from  its  two  ven- 
tricles into  the  pulmonary  artery  and  the  aor- 
ta, and  then  as  relaxing  itself  and  receiving  a 
fresh  supply  from  two  large  veins,  which  are 
the  pulmonary  vein  and  the  vena  cava.  We 
will  now  point  out  the  principal  distributions 
of  these  vessels. 

The  pulmonary  artery  arises  from  the  right 
ventricle  by  a large  trunk,  which  soon  divides 
into  two  considerable  branches,  which  pass  to 
the  right  and  left  lobes  of  the  lungs  ; each  of 
these  branches  is  afterwards  divided  and  sub- 
divided into  an  infinite  number  of  branches  and 
ramifications,  which  extend  through  the  whole 
substance  of  the  lungs  ; and  from  these  branch- 
es the  blood  is  returned  by  the  veins,  which, 
contrary  to  the  course  of  the  arteries,  begin 
by  very  minute  canals,  and  gradually  become 
larger,  forming  at  length  four  large  trunks 
called  pulmonary  veins , which  terminate  in  the 
left  auricle  by  one  common  opening,  from 
whence  the  blood  passes  into  the  left  ventricle. 
From  this  same  ventricle  arises  the  aorta  or 
great  artery , which  at  its  beginning  is  nearly 


343 


Of  the  Thorax. 

an  inch  in  diameter ; it  soon  sends  off  two 
branches,  the  coronaries , which  go  to  be  dis- 
tributed to  the  heart  and  its  auricles.  After 
this,  at  or  about  the  third  or  fourth  vertebra 
of  the  back,  it  makes  a considerable  curva- 
ture ; from  this  curvature  * arise  three  arte- 
ries; one  of  which  soon  divides  into  two  branch- 
es. The  first  two  are  the  left  subclavian 
and  the  left  carotid,  and  the  third  is  a com- 
mon trunk  to  the  right  subclavian  and  right 
carotid  ; though  sometimes  both  the  carotids 
arise  distinctly  from  the  aorta. 

The  two  carotids  ascend  within  the  subcla- 
vians,  along  the  sides  of  the  trachea ; and 
when  they  have  reached  the  larynx,  divide 
into  two  principal  branches,  the  internal  and 
external  carotid.  The  first  of  these  runs  a lit- 
tle way  backwards  in  a bending  direction  ; and 
having  reached  the  under  part  of  the  ear,  pass- 
es through  the  canal  into  the  os  petrosum, 
and  entering  into  the  cavity  of  the  cranium,  is 
distributed  to  the  brain  and  the  membranes 
which  envelope  it,  and  likewise  to  the  eye. 
The  external  carotid  divides  into  several 
branches,  which  are  distributed  to  the  larynx, 
pharynx,  and  other  parts  of  the  neck ; and  to 
the  jaws,  lips,  tongue,  eyes,  temples,  and  all 
the  external  parts  of  the  head. 

* Anatomists  usually  call  the  upper  part  of  this  curvature 
aorta  ascendens  ; and  the  other  part  of  the  artery  to  its  division  at 
the  iliacs,  aorta  descendens : but  they  differ  about  the  place  where 
this  distinction  is  to  be  introduced  ; and  it  seems  sufficiently  to 
answer  every  purpose,  to  speak  only  of  the  aorta  and  its  curva- 
ture . 


344 


Of  the  Thorax. 


Each  subclavian  is  likewise  divided  into  a 
great  number  of  branches.  It  sends  off  the 
vertebral  artery , which  passes  through  the 
openings  we  see  at  the  bottom  of  the  transverse 
processes  of  the  vertebras  of  the  neck,  and  in 
its  course  sends  off  many  ramifications  to  the 
neighbouring  parts.  Some  of  its  branches  are 
distributed  to  the  spinal  marrow,  and  after  a 
considerable  inflection  it  enters  into  the  crani- 
um, and  is  distributed  to  the  brain.  The  sub- 
clavian likewise  sends  off  branches  to  the  mus- 
cles of  the  neck  and  scapula ; and  the  medias- 
tinum, thymus,  pericardium,  diaphragm,  the 
breasts,  and  the  muscles  of  the  thorax,  and 
even  of  the  abdomen,  derive  branches  from 
the  subclavian,  which  are  distinguished  by 
different  names,  alluding  to  the  parts  to  which 
they  are  distributed ; as  the  mammary , the 
phrenic , the  intercostal , &c.  But  notwithstand- 
ing the  great  number  of  branches  which  have 
been  described  as  arising  from  the  subclavian, 
it  is  still  a considerable  artery  when  it  reach- 
es the  axilla , where  it  drops  its  former  name, 
which  alludes  to  its  passage  under  the  clavi- 
cle, and  is  called  the  axillary  artery ; from 
which  a variety  of  branches  are  distributed  to 
the  muscles  of  the  breast,  scapula,  and  arm. — 
But  its  main  trunk  taking  the  name  of  brachi- 
alis , runs  along  on  the  inside  of  the  arm  near 
the  os  humeri,  till  it  reaches  the  joint  of  the 
fore-arm,  and  then  it  divides  into  two  branch- 
es. This  division  however  is  different  in  dif- 
ferent subjects;  for  in  some  it  takes  place  high- 
er up  and  in  others  lower  down.  When  it 
happens  to  divide  above  the  joint,  it  may  be 


345 


Of  the  Thorax. 

considered  as  a happy  disposition  in  case  of  an 
accident  by  bleeding ; for  supposing  the  artery 
to  be  unfortunately  punctured  by  the  lancet, 
and  that  the  haemorrhage  could  only  be  stop- 
ped by  making  a ligature  on  the  vessel,  one 
branch  would  remain  unhurt,  through  which 
the  blood  would  pass  uninterrupted  to  the  fore- 
arm and  hand.  One  of  the  two  branches  of 
the  brachialis  plunges  down  under  the  flexor 
muscles,  and  runs  along  the  edge  of  the  ulna  ; 
while  the  other  is  carried  along  the  outer  sur- 
face of  the  radius,  and  is  easily  felt  at  the 
wrist,  where  it  is  only  covered  by  the  common 
integuments.  Both  these  branches  commonly 
unite  in  the  palm  of  the  hand,  and  form  an  ar- 
terial arch  from  whence  branches  are  detached 
to  the  fingers. 

The  aorta , after  having  given  olf  at  its  cur- 
vature the  carotids  and  subclavians  which  con- 
vey blood  to  all  the  upper  parts  of  the  body, 
descends  upon  the  bodies  of  the  vertebras  a lit- 
tle to  the  left,  as  far  as  the  os  sacrum,  where 
it  drops  the  name  of  aorta , and  divides  into 
two  considerable  branches.  In  this  course, 
from  its  curvature  to  its  bifurcation,  it  sends 
olf  several  arteries  in  the  following  order:  1. 
One  or  two  little  arteries,  first  demonstrated 
by  Ruysch  as  going  to  the  bronchi,  and  called 
arteria  bronchinaies  Ruyschii.  2.  The  arteriae 
cesophageae.  These  are  commonly  three  or 
four  in  number.  They  arise  from  the  fore- 
part of  the  aorta,  and  are  distributed  chiefly  to 
the  (Esophagus.  3.  The  inferior  intercostal 
arteries,  which  are  distributed  between  the 
fibs  in  the  same  manner  as  the  arteries  of  the 

X x 


346 


Of  the  Thorax. 


three  or  four  superior  ribs  are,  which  are  de- 
rived from  the  subclavian.  These  arteries 
send  off  branches  to  the  medulla  spinalis.  4. 
The  diaphragmatic  or  inferior  phrenic  arteries, 
which  go  to  tne  diaphragm,  stomach,  omentum, 
duodenum,  pancreas,  spleen,  liver,  and  gall- 
bladder. 5.  The  cceliarc,  which  sends  off  the 
coronary-stomachic,  the  splenic,  and  the  hepa- 
tic artery.  6.  The  superior  mesenteric  artery, 
which  is  distributed  to  the  mesentery  and  small 
intestines,  7.  The  emulgents,  which  go  to  the 
kidneys.  8.  The  arteries,  which  are  distri- 
buted to  the  glandulae  renales,  9.  The  sper- 
matic. 10.  The  inferior  mesenteric  artery, 
which  ramifies  through  the  lower  portion  of  the 
mesentery  and  the  large  intestines. — A branch 
of  this  artery  which  goes  to  the  rectum  is  call- 
ed the  internal  hemorrhoidal.  11.  The  lum- 
bar arteries,  and  a very  small  branch  called 
the  sacra , which  are  distributed  to  the  mus- 
cles of  the  loins  and  abdomen,  and  to  the  os 
sacrum  and  medulla  spinalis. 

The  trunk  of  the  aorta,  when  it  has  reached 
the  last  vertebra  lumborum,  or  the  os  sacrum, 
drops  the  name  of  aorta , and  separates  into  two 
forked  branches  called  the  iliacs.  Each  of 
these  soon  divides  into  two  branches  ; one  of 
which  is  called  the  internal  iliac , or  hypogas- 
tric artery , and  is  distributed  upon  the  contents 
of  the  pelvis  and  upon  the  muscles  on  its  out- 
er side.  One  branch,  called  pudenda  commu- 
nis, sends  small  ramifications  to  the  end  of 
the  rectum  under  the  name  of  hannorrhoulales 
extern ce,  and  is  afterwards  distributed  upon 
the  penis.  The  other  branch,  the  external  ill- 


347 


Of  the  Thorax. 

ac,  after  having  given  off  the  circumflex  artery 
of  the  os  ilium  and  the  epigastric,  which  is 
distributed  to  the  recti-muscles,  passes  out  oi 
the  abdomen  under  Poupart’s  ligament,  and 
takes  the  name  of  crural  artery.  It  descends 
on  the  inner  part  of  the  thigh  close  to  the  os 
femoris,  sending  off  branches  to  the  muscles, 
and  then  sinking  deeper  in  the  hind  part  of 
the  thigh,  reaches  the  ham,  where  it  takes 
the  name  of  popliteal : after  this  it  separates  into 
two  considerable  branches  ; one  of  which  is 
called  the  anterior  tibial  artery  ; the  other  di- 
vides into  two  branches,  and  these  arteries  all 
go  to  be  distributed  to  the  leg  and  foot. 

The  blood,  which  is  thus  distributed  by  the 
aorta  to  all  parts  of  the  body,  is  brought  back 
by  the  veins,  which  are  supposed  to  be  conti- 
nued from  the  ultimate  branches  of  arteries  ; 
and  uniting  together  as  they  approach  the 
heart,  at  length  form  the  large  trunks,  the  ve- 
na cava  ascendens,  and  vena  cava  descendens. 

All  the  veins  which  bring  back  the  blood 
from  the  upper  extremities,  and  from  the  head 
and  breast,  pass  into  the  vena  cava  descendens  ; 
and  those  which  return  it  from  the  lower  parts 
of  the  body  terminate  in  the  vena  cava  ascen- 
dens ; and  these  two  cavas  uniting  together  as 
they  approach  the  heart,  open  by, one  common 
orifice  into  the  left  auricle. 

It  does  not  here  seem  to  be  necessary  to  fol- 
low the  different  divisions  of  the  veins  as  we 
did  those  of  the  arteries  ; and  it  will  be  suffi- 
cient to  remark,  that  in  general  every  artery  is 
accompanied  by  its  vein,  and  that  both  are  dis- 
tinguished by  the  same  name.  But,  like  many 


348 


Of  the  Thorax . 


other  general  rules,  this  too  has  its  excep- 
tions.* The  veins  for  instance,  which  accom- 
pany the  external  and  internal  carotid,  are  not 
called  the  carotid  veins , but  the  external  and  in- 
ternal jugular. — In  the  thorax,  there  is  a vein 
distinguished  by  a proper  name,  and  this  is  the 
azygos , or  vena  sine  pari.  This  vein,  which 
is  a pretty  considerable  one,  runs  along  by  the 
right  side  of  the  vertebras  of  the  back,  and  is 
chiefly  destined  to  receive  the  blood  from  the 
intercostals  on  that  side,  and  from  the  lower 
half  of  those  on  the  left  side,  and  to  convey  it 
into' the  vena  cava  descendens.  In  the  abdo- 
men we  meet  with  a vein,  which  is  still  a more 
remarkable  one,  and  this  is  the  vena  porta , 
which  performs  the  office  both  of  an  artery  and 
a vein.  It  is  formed  by  a re-union  of  all  the 
veins  which  come  from  the  stomach,  intestines, 
omentum,  pancreas,  and  spleen,  so  as  to  com- 
pose one  great  trunk,  which  goes  to  ramify 
through  the  liver ; and  after  having  deposited 
the  bile,  its  ramifications  unite  and  bring  back 
into  the  vena  cava,  not  only  the  blood  which 
the  vena  portae  had  carried  into  the  liver,  but 
likewise  the  blood  from  the  hepatic  artery. 
Every  artery  has  a vein  which  corresponds  with 
it ; but  the  trunks  and  branches  of  the  veins 
are  more  numerous  than  those  of  the  arteries. 
— The  reasons  for  this  disposition  are  perhaps 
more  difficult  to  be  explained  ; the  blood  in  its 
course  through  the  veins  is  much  farther  re- 
moved from  the  source  and  cause  of  its  mo- 

* In  the  extremities,  some  of  the  deep-seated  veins,  and  all 
the  superficial  ones,  take  a course  different  from  that  of  the 
arteries. 


Of  the  Thorax. 


349 


tion,  which  are  in  the  heart,  than  it  was  when 
in  the  arteries  ; so  that  its  course  is  consequent- 
ly less  rapid,  and  enough  of  it  could  not  pos- 
sibly be  brought  back  to  the  heart  in  the  mo- 
ment of  its  dilatation,  to  equal  the  quantity 
which  is  driven  into  the  arteries  from  the  two 
ventricles,  at  the  time  they  contract ; and  the 
equilibrium  which  is  so  essential  to  the  conti- 
nuance of  life  and  health  would  consequently 
be  destroyed,  if  the  capacity  of  the  veins  did 
not  exceed  that  of  the  arteries,  in  the  same  pro- 
portion that  the  rapidity  of  the  blood’s  motion 
through  the  arteries  exceeds  that  of  its  return 
through  the  veins. 

A large  artery  ramifying  through  the  body, 
and  continued  to  the  minute  branches  of  veins, 
which  gradually  unite  together  to  form  a large 
trunk,  may  be  compared  to  two  trees  united  to 
each  other  at  their  tops  ; or  rather  as  having 
their  ramifications  so  disposed  that  the  two 
trunks  terminate  in  one  common  point;  and  if  we 
farther  suppose,  that  both  these  trunks  and  their 
branches  are  hollow,  and  that  a fiuid  is  inces- 
santly circulated  through  them,  by  entering  in- 
to one  of  the  trunks  and  returning  through  the 
other,  we  shall  be  enabled  to  conceive  how  the 
blood  is  circulated  through  the  vessels  of  the 
human  body. 

Every  trunk  of  an  artery,  before  it  divides, 
is  nearly  cylindrical,  or  of  equal  diameter 
through  its  whole  length,  and  so  are  all  its 
branches  when  examined  separately.  But  eve- 
ry trunk  seems  to  contain  less  blood  than  the 
many  branches  do  into  which  that  trunk  sepa- 
rates ; and  each  of  these  branches  probably 


350 


Of  the  Thorax. 


contains  less  blood  than  the  ramifications  do 
into  which  it  is  subdivided  : and  it  is  the  same 
with  the  veins ; the  volume  of  their  several 
ramifications,  when  considered  together,  being 
found  to  exceed  that  of  the  great  trunk  which 
they  form  by  their  union. 

The  return  of  the  blood  through  the  veins 
to  the  heart,  is  promoted  by  the  action  of  the 
muscles,  and  the  pulsation  of  the  arteries. 
And  this  return  is  likewise  greatly  assisted  by 
the  valves  which  are  to  be  met  with  in  the 
veins,  and  which  constitute  one  of  the  great 
distinctions  between  them  and  the  arteries. 
These  valves,  which  are  supposed  to  be  form- 
ed by  the  inner  coat  of  the  veins,  permit  the 
blood  to  flow  from  the  extremities  towards  the 
heart,  but  oppose  its  return.  They  are  most 
frequent  in  the  smaller  veins.  As  the  column 
of  blood  increases,  they  seem  to  become  less 
necessary ; and  therefore  in  the  vena  cava  as- 
cendens,  we  meet  with  only  one  valve,  which 
is  near  its  origin. 

The  arteries  are  composed  of  several  tunics. 
Some  writers  enumerate  five  of  these  tunics  ; 
but  perhaps  we  may  more  properly  reckon  only 
three,  viz.  the  nervous , muscular , and  cuticular 
coats.  The  veins  are  by  some  anatomists  de- 
scribed as  having  the  same  number  of  coats  as 
the  arteries ; but  as  they  do  not  seem  to  be  ir- 
ritable, we  cannot  with  propriety  suppose  them 
to  have  a muscular  tunic.  We  are  aware  of 
Dr.  Verschuir’s*  experiments  to  prove  that 
the  jugular  and  some  other  veins  possess  a 


* De  Arteriarum  et  Venarum  vi  irritabili,  4to. 


Of  the  Thorax. 


351 


certain  degree  of  irritability;  but  it  is  cer- 
tain, that  his  experiments,  repeated  by  others, 
have  produced  a different  result ; and  even  he 
himself  allows,  that  sometimes  he  was  unable 
to  distinguish  any  such  property  in  the  veins. 
Both  these  series  of  vessels  are  nourished  by 
still  more  minute  arteries  and  veins,  which  are 
seen  creeping  over  their  coats,  and  ramifying 
through  their  whole  substance,  and  are  called 
vasa  vasorum : they  have  likewise  many  mi- 
nute branches  of  nerves. 

The  arteries  are  much  stronger  than  the 
veins,  and  they  seem  to  require  this  force  to 
be  enabled  to  resist  the  impetus  with  which  the 
blood  circulates  through  them,  and  to  impel  it 
on  towards  the  veins. 

When  the  heart  contracts,  it  impels  the  blood 
into  the  arteries,  and  sensibly  distends  them  ; 
and  these  vessels  again  contract,  as  the  heart 
becomes  relaxed  to  receive  more  blood  from 
the  auricles  : so  that  the  cause  of  the  contrac- 
tion and  dilatation  of  the  arteries  seems  to  be 
easy  to  be  understood,  being  owing  in  part  to 
their  own  contractile  power,  and  in  part  to  the 
action  of  the  heart ; but  in  the  veins , the  effects 
of  this  impulse  not  being  so  sensibly  felt,  and 
the  vessels  themselves  having  little  or  no  con- 
tractile power,  the  blood  seems  to  flow  in  a 
constant  and  equal  stream  : and  this,  together 
with  its  passing  gradually  from  a small  channel 
into  a larger  one,  seems  to  be  the  reason  why 
the  veins  have  no  pulsatory  motion,  except  the 
large  ones  near  the  heart ; arid  in  these  it  seems 
to  be  occasioned  by  the  motion  of  the  dia- 
phragm, and  by  the  regurgitation  of  the  blood 
in  the  cavas. 


352 


Of  the  Thorax. 


Sect.  XII.  Of  the  Action  of  the  Heart , 
Auricles , and  Arteries. 

The  heart,  at  the  time  it  contracts,  drives 
the  blood  from  its  ventricles  into  the  arteries ; 
and  the  arteries  being  thus  filled  and  distended, 
are  naturally  inclined  to  contract  the  moment 
the  heart  begins  to  dilate,  and  ceases  to  supply 
them  with  blood.  These  alternate  motions  of 
contraction  and  dilatation  of  the  heart  and  ar- 
teries, are  distinguished  by  the  names  of  systole 
and  diastole.  When  the  heart  is  in  a state  of 
contraction  or  systole,  the  arteries  are  at  that 
instant  distended  with  blood,  and  in  their 
diastole  ; and  it  is  in  this  state  we  feel  their 
pulsatory  motion  which  we  call  the  pulse. 
When  the  heart  dilates,  and  the  arteries  contract, 
the  blood  is  impelled  onwards  into  the  veins 
through  which  it  is  returned  back  to  the  heart. 
While  the  heart,  however,  is  in  its  systole,  the 
blood  cannot  pass  from  the  veins  into  the 
ventricles,  but  is  detained  in  the  auricles,  which 
are  two  reservoirs  formed  for  this  use,  till  the 
diastole,  or  dilatation  of  the  heart,  takes  place  ; 
and  then  the  distended  auricles  contract,  and 
drive  the  blood  into  the  ventricles  ; so  that  the 
auricles  have  an  alternate  systole  and  diastole 
as  well  as  the  heart. 

Although  both  the  ventricles  of  the  heart 
contract  at  the  same  time,  yet  the  blood  pass- 
es from  one  to  the  other.  In  the  same  mo- 
ment, for  instance,  that  the  left  ventricle 
drives  the  blood  into  the  aorta,  the  right  ven- 
tricle impels  it  into  the  pulmonary  artery, 


Of  the  Thorax. 


353 


which  is  distributed  through  all  the  substance 
of  the  lungs.  The  blood  is  afterwards  brought 
back  into  the  left  ventricle  by  the  pulmonary 
vein,  at  the  same  time  that  the  blood  is  returned 
by  the  cavas,  into  the  right  ventricle,  from  ail 
the  other  parts  of  the  body. 

This  seems  to  be  the  mode  of  action  of  the 
heart  and  its  vessels  ; but  the  cause  of  this  action 
has,  like  all  other  intricate  and  interesting  sub- 
jects, been  differently  explained.  It  seems  to 
depend  on  the  stimulus  made  on  the  different 
parts  of  the  heart  by  the  blood  itself,  which  by 
its  quantity  and  heat,  or  other  properties,*  is 
perhaps  capable  of  first  exciting  that  motion, 
which  is  afterwards  continued  through  life,  in- 
dependent of  the  will,  by  a regular  return  of 
blood  to  the  auricles,  in  a quantity  proportion- 
ed to  that  which  is  thrown  into  the  arteries. 

The  heart  possesses  the  vis  insita , or  prin- 
ciple of  irritability,  in  a much  greater  degree 
than  any  other  muscle  of  the  body.  The  pulse 
is  quicker  in  young  than  in  old  subjects,  be- 
cause the  former  are  cat.  par.  more  irritable 
than  the  latter.  Upon  the  same  principle  we 
may  explain,  why  the  pulse  is  constantly  quick- 
er in  weak  than  in  robust  persons. 

Y y 

* Dr.  Harvey  long  ago  suggested,  that  the  blood  is  possessed 
of  a living  principle  ; and  Mr.  J.  Hunter  has  lately  endeavoured 
to  revive  this  doctrine  : in  support  of  which  he  has  adduced  many 
ingenious  arguments.  The  subject  is  a curious  one,  and  deferves 
to  be  prosecuted  as  an  inquiry  which  cannot  but  be  interesting 
to  physiologists. 


Of  the  Thorax. 


354 


Sect.  XIII.  Of  the  Circulation. 

After  what  has  been  observed  of  the 
structure  and  action  of  the  heart  and  its 
auricles,  and  likewise  of  the  arteries  and  veins, 
there  seem  to  be  but  very  few  arguments 
required  to  demonstrate  the  circulation  of  the 
blood , which  has  long  since  been  established 
as  a medical  truth.  This  circulation  may  be 
defined  to  be  a perpetual  motion  of  the  blood, 
in  consequence  of  the  action  of  the  heart  and 
arteries,  which  impel  it  through  all  the  parts 
of  the  body,  from  whence  it  is  brought  back 
by  the  veins  of  the  heart. 

A very  satisfactory  proof  of  this  circulation, 
and  a proof  easy  to  be  understood,  may  be  de- 
duced from  the  different  effects  of  pressure  on 
an  artery  and  a vein.  If  a ligature,  for  instance, 
is  passed  round  an  artery,  the  vessel  swells 
considerably  between  the  ligature  and  the 
heart ; whereas  if  we  tie  up  a vein,  it  only  be- 
comes filled  between  the  extremity  and  the 
ligature,  and  this  is  what  we  every  day  observe 
in  bleeding.  The  ligature  we  pass  round  the 
arm  on  these  occasions,  compresses  the  super- 
ficial veins ; and  the  return  of  the  blood 
through  them  being  impeded,  they  become  dis- 
tended. When  the  ligature  is  too  loose,  the 
veins  are  not  sufficiently  compressed,  and  the 
blood  continues  its  progress  towards  the  heart ; 
and,  on  the  contrary,  when  it  is  made  too  tight, 
the  arteries  themselves  become  compressed ; 


.355 


Of  the  Thorax. 

and  the  flow  of  the  blood  through  them  being 
impeded,  the  veins  cannot  be  distended. 

Another  phenomenon,  which  effectually 
proves  the  circulation,  is  the  loss  of  blood  that 
every  living  animal  sustains  by  opening  only 
a single  artery  of  a moderate  size ; for  it  con- 
tinues to  flow  from  the  wounded  vessel  till  the 
equilibrium  is  destroyed  which  is  essential  to 
life.  This  truth  was  not  unknown  to  the  an- 
cients ; and  it  seems  strange  that  it  did  not 
lead  them  to  a knowledge  of  the  circulation,  as 
it  sufficiently  proves,  that  all  the  other  vessels 
must  communicate  with  that  which  is  opened. 
Galen,  who  lived  more  than  1500  years  ago, 
drew  this  conclusion  from  it ; and  if  wre  far- 
ther observe,  that  he  describes  (after  Erasis- 
tratus,  who  flourished  about  450  years  before 
him)  the  several  valves  of  the  heart,  and  de- 
termines their  disposition  and  uses,  it  will  ap- 
pear wonderful,  that  a period  of  near  2000 
years  should  afterwards  elapse  before  the  true 
course  of  the  blood  was  ascertained.  This 
discovery,  for  which  we  are  indebted  to  the 
immortal  Harvey,  has  thrown  new  lights  on 
physiology  and  the  doctrine  of  diseases,  and 
constitutes  one  of  the  most  important  periods 
of  anatomical  history. 


Sect.  XIV.  Of  the  Nature  of  the  Blood. 

Blood,  recently  drawn  from  a vein  into  a 
bason,  would  seem  to  be  an  homogeneous  fluid 


356 


Of  the  Thorax. 

of  a red  colour  ;*  but  when  suffered  to  rest,  it 
soon  coagulates,  and  divides  into  two  parts, 
which  are  distinguished  by  the  names  of  cras- 
samentum  and  serum.  The  crassamentum  is 
the  red  coagulum,  and  the  serum  is  the  water 
in  which  it  floats.  Each  of  these  may  be  again 
separated  into  two  others ; for  the  crassamen- 
tum, by  being  repeatedly  washed  in  warm  wa- 
ter, gives  out  all  its  red  globules,  and  what 
remains  appears  to  be  composed  of  the  coagu- 
lable  lymph, f which  is  a gelatinous  substance, 
capable  of  being  hardened  by  fire  till  it  becomes 
perfectly  horny : and  if  we  expose  the  serum 
to  a certain  degree  of  heat,  part  of  it  will  be 
found  to  coagulate  like  the  white  of  an  egg, 
and  there  will  remain  a clear  and  limpid  water, 
resembling  urine  both  in  its  appearance  and 
smell. 

The  serum  and  crassamentum  differ  in 
their  proportion  in  different  constitutions ; in 
a strong  person,  the  crassamentum  is  in  a great- 
er proportion  to  the  serum  than  in  a weak 
one  ;f  and  the  same  difference  is  found  to  take 
place  in  diseases. $ 

* The  blood,  as  it  flows  through  the  arteries,  is  observed  to 
be  more  florid  than  it  is  in  the  veins  ; and  this  redness  is  acquir- 
ed in  its  passage  through  the  lungs.  Vid.  feet.  vii. 

-f*  It  may  not  be  improper  to  observe,  that  till  of  late  the  coa- 
gu/able  lymph  has  been  confounded  with  the  serum  of  the  blood, 
which  contains  a substance  that  is  likewise  coagulable,  though 
only  when  exposed  to  heat,  or  combined  with  certain  chemical 
substances  ; whereas  the  other  coagulates  spontaneously  when 
exposed  to  the  air  or  to  rest. 

J Hewson’s  Experim.  Enq.  Part  I. 

$ When  the  blood  separates  into  serum  and  crassamentum,  if  the 
latter  be  covered  with  a crust  of  a whitish  or  buff  colour,  it  has 
been  usually  considered  as  a certain  proof  of  the  blood’s  being  in 
a state  of  too  great  viscidity.  This  appearance  commonly  taking 
place  in  inflammatory  diseases,  has  long  served  to  confirm  the 


Of  the  Thorax. 


357 


Sect.  XV.  Of  Nutrition. 

The  variety  of  functions  which  we  have  de- 
scribed as  being  incessantly  performed  by  the 
living  body,  and  the  continual  circulation  of  the 
blood  through  it,  must  necessarily  occasion  a 
constant  dissipation  of  the  several  parts  which 
enter  into  its  composition.  In  speaking  of  the 
insensible  perspiration,  we  observed  how  much 
was  incessantly  passing  off  from  the  lungs  and 
the  surface  of  the  skin.  The  discharge  by 
urine  is  likewise  every  day  considerable  ; and 
great  part  of  the  bile,  saliva,  Stc.  are  excluded 
by  stool.  But  the  solid,  as  well  as  the  fluid 
parts  of  the  body,  require  a constant  renew  al 
of  nutritious  particles.  They  are  exposed  to 
the  attrition  of  the  fluids  which  are  circulated 
through  them ; and  the  contraction  and  relax- 
ation they  repeat  so  many  thousand  times  in 
every  day,  would  necessarily  occasion  a disso- 
lution of  the  machine,  if  the  renewal  was  not 
proportioned  to  the  waste. 

It  is  easy  to  conceive  how  the  chyle  formed 
from  the  aliment  is  assimilated  into  the  nature 

theory  which  ascribes  the  cause  of  inflammation  to  lentor  and  ob- 
structions. But  from  the  late  Mr  Hewson’s  experiments  it  ap- 
pears, that  when  the  action  of  the  arteries  is  increased,  the  blood, 
instead  of  being  more  viscid,  is,  on  the  contrary,  more  fluid  than 
in  the  ordinary  state,  previous  to  inflammation  ; and  that  in  con- 
sequence of  this,  the  coagulable  lymph  suffers  the  red  globules, 
which  are  the  heaviest  part  of  the  blood,  to  fall  down  to  the  bot- 
tom before  it  coagulates  ; so  that  the  crassamentum  is  divided 
into  two  parts : one  of  which  is  found  to  consist  of  the  coagula- 
ble lymph  alone  (in  this  case-  termed  the  bvjf)  ; and  the  other, 
partly  of  this  and  partly  of  the  red  globules. 


358 


Of  the  Thorax. 


of  blood,  and  repairs  the  loss  of  the  fluid  parts 
of  our  body  ; but  how  the  solids  are  renewed, 
has  never  yet  been  satisfactorily  explained. 
The  nutritious  parts  of  the  blood  are  probably 
deposited  by  the  arteries  by  exsudation  through 
their  pores  into  the  tela  cellulosa ; and  as  the 
solid  parts  of  the  body  are  in  the  embryo  only 
a kind  of  jelly,  which  gradually  acquires  the 
degree  of  consistence  they  are  found  to  have 
when  the  body  arrives  at  a more  advanced 
age  ; and  these  same  parts  which  consist  of 
bones,  cartilages,  ligaments,  muscles,  Ike.  are 
sometimes  reduced  again  by  disease  to  a gela- 
tinous state ; we  may,  with  some  degree  of 
probability,  consider  the  coagulable  lymph  as 
the  source  of  nutrition. 

If  the  supply  of  nourishment  exceeds  the 
degree  of  waste,  the  body  increases  ; and  this 
happens  in  infancy  and  in  youth  : for  at  those 
periods,  but  more  particularly  the  former  one, 
the  fluids  bear  a large  proportion  to  the  solids  ; 
and  the  fibres  being  soft  and  yielding,  are  pro- 
portionably  more  capable  of  extension  and  in- 
crease. But  when  the  supply  of  nutrition  only 
equals  the  waste,  we  neither  increase  nor  de- 
crease ; and  we  find  this  to  be  the  case  when 
the  body  has  attained  its  full  growth  or  acme : 
for  the  solids  having  then  acquired  a certain 
degree  of  firmness  and  rigidity,  do  not  permit 
a farther  increase  of  the  body.  But  as  we  ap- 
proach to  old  age,  rigidity  begins  to  be  in  ex- 
cess, and  the  fluids  * bear  a much  less  propor- 

* As  the  fluids  become  less  in  proportion  to  the  solids,  their 
acrimony  is  found  to  increase  ; and  this  may  perhaps  compen- 
sate for  the  want  of  fluidity  in  the  blood  by  diminishing  its  co- 
hesion. 


Of  the  Thorax . 


359 - 


lion  to  the  solids  than  before.  The  dissipation 
of  the  body  is  greater  than  the  supply  of  nour- 
ishment; many  of  the  smaller  vessels  become 
gradually  impervious  ;*  and  the  fibres  losing 
their  moisture  and  their  elasticity,  appear  flac- 
cid and  wrinkled.  1 he  lilies  and  the  roses  dis- 
appear, because  the  fluids  by  which  they  were 
produced  can  no  longer  reach  the  extremities 
of  the  capillary  vessels  of  the  skin.  As  these 
changes  take  place,  the  nervous  power  being 
proportionably  weakened,  the  irritability  and 
sensibility  of  the  body,  which  were  formerly 
so  remarkable,  are  greatly  diminished  ; and  in 
advanced  life,  the  hearing,  the  eye-sight,  and 
all  the  other  senses,  become  gradually  im- 
paired. 

Sect.  XVI.  Of  the  Glands  and  Secretions . 

The  glands  are  commonly  understood  to  be 
small,  roundish,  t,r  oval  bodies  formed  by  the 
convolution  of  a great  number  of  vessels,  and 
destined  to  separate  particular  humours  from 
the  mass  of  blood. 

They  are  usually  divided  into  two  classes ; 
but  it  seems  more  proper  to  distinguish  three 
kinds  of  glands,  viz.  the  mucous,  conglobate, 
and  conglomerate. 

The  mucous  glands , or  follicles,  as  they  are 
most  commonly  called,  are  small  cylindrical 

* In  infancy,  the  arteries  are  numerous  and  large  in  respect 
to  the  veins,  and  the  lymphatic  glands  are  larger  than  at  any 
other  time  of  life  ; whereas,  in  old  age,  the  capacity  of  the  ve- 
nous system  exceeds  that  of  the  arteries,  and  the  lymphatic  sys- 
tem almost  disappears. 


360 


Of  the  Thorax. 

tubes  continued  from  the  ends  of  arteries.  In 
some  parts  of  the  body,  as  in  the  tonsils,  for 
example,  several  of  these  follicles  may  be  seen 
folded  together  in  one  common  covering,  and 
opening  into  one  common  sinus.  These  folli- 
cles are  the  vessels  that  secrete  and  pour  out 
mucus  in  the  mouth,  oesophagus,  stomach,  in- 
testines, and  other  parts  of  the  body. 

The  conglobate  glands  are  peculiar  to  the 
lymphatic  system.  Every  lymphatic  vein  pass- 
es through  a gland  of  this  kind  in  its  way  to 
the  thoracic  duct.  They  are  met  with  in  dif- 
ferent parts  of  the  body,  particularly  in  the 
axilla,  groin,  and  mesentery,  and  are  either 
solitary  or  in  distinct  clusters. 

The  conglomerate  glands  are  of  much  great- 
er bulk  than  the  conglobate,  and  seem  to  be  an 
assemblage  of  many  smaller  glands.  Of  this 
kind  are  the  liver,  kidneys,  fkc.  Some  of  them, 
as  the  pancreas,  parotids,  fkc.  have  a granu- 
lated appearance.  All  these  conglomerate 
glands  are  plentifully  supplied  with  blood-ves- 
sels ; but  their  nerves  are  in  general  very  mi- 
nute, and  few  in  number.  Each  little  granu- 
lated portion  furnishes  a small  tube,  which 
unites  with  other  similar  ducts,  to  form  the 
common  excretory  duct  of  the  gland. 

The  principal  glands,  and  the  humours 
they  secrete,  have  been  already  described  in 
different  parts  of  this  work;  and  there  only 
remains  for  us  to  examine  the  general  structure 
of  the  glands,  and  to  explain  the  mechanism 
of  secretion.  On  the  first  of  these  subjects 
two  different  systems  have  been  formed ; each 
of  which  has  had,  and  still  continues  to  have, 


361 


Of  the  Thorax . 

its  adherents.  One  of  these  systems'  was  ad- 
vanced by  Malpighi,  who  supposed  that  an  ar- 
tery entering  into  a gland  ramifies  very  mi- 
nutely through  its  whole  substance  ; and  that 
its  branches  ultimately  terminate  in  a vesicu- 
lar cavity  or  follicle,  from  whence  the  secreted 
fluid  passes  out  through  the  excretory  duct. 
This  doctrine  at  first  met  with  few  opponents  ; 
but  the  celebrated  Ruysch,  who  first  attempt- 
ed minute  injections  with  wax,  afterwards  dis- 
puted the  existence  of  these  follicles  and  as- 
serted, that  every  gland  appears  to  be  a con- 
tinued series  of  vessels,  which  after  being  re- 
peatedly convoluted  in  their  course  through 
its  substance,  at  length  terminate  in  the  ex- 
cretory duct.  Anatomists  are  still  divided  be- 
tween these  two  systems : that  of  Malpighi, 
however,  seems  to  be  the  best  founded. 

The  mode  of  secretion  has  been  explained 
in  a variety  of  ways,  and  they  are  all  perfectly 
hypothetical.  In  such  an  inquiry  it  is  natural 
to  ask,  how  one  gland  constantly  separates  a 
particular  humour,  while  another  gland  se- 
cretes one  of  a very  different  nature  from  the 
blood ? The  bile,  for  instance,  is  separated 
by  the  liver,  and  the  urine  by  the  kidneys..  Are 
these  secretions  to  be  imputed  to  any  particu- 
lar dispositions  in  the  fluids,  or  is  their  cause 
to  be  looked  for  in  the  solids  ? 

It  has  been  supposed,  that  every  gland  con- 
tains within  itself  a fermenting  principle,  by 
which  it  is  enabled  to  change  the  nature  of  the 
blood  it  receives,  and  to  endue  it  with  a par- 
ticular property.  So  that,  according  to  this 
system,  the  blood,  as  it  circulates  through  the 

Z z 


362 


Of  the  Thorax. 

kidneys,  becomes  mixed  with  the  fermenting 
principle  of  those  glands,  and  a part  of  it  is 
converted  into  urine  ; and  again,  in  the  liver, 
in  the  salival  and  other  glands,  the  bile,  the 
saliva,  and  other  juices,  are  generated  from  a 
similar  cause.  But  it  seems  to  be  impossible 
for  any  liquor  to  be  confined  in  a place  expos- 
ed to  the  circulation,  without  being  carried 
away  by  the  torrent  of  blood,  every  part  of 
which  would  be  equally  affected  ; and  this  sys- 
tem of  fermentation  has  long  been  rejected  as 
vague  and  chimerical.  But  as  the  cause  of  se- 
cretion continued  to  be  looked  for  in  the  fluids, 
the  former  system  was  succeeded  by  another, 
in  which  recourse  was  had  to  the  analogy  of 
the  humours.  It  was  observed,  that  if  paper 
is  moistened  with  water,  and  oil  and  water  are 
afterwards  poured  upon  it,  that  the  water  only 
will  be  permitted  to  pass  through  it;  but  that, 
on  the  other  hand,  if  the  paper  has  been  pre- 
viously soaked  in  oil  instead  of  water,  the  oil 
only,  and  not  the  water  will  be  filtered  through 
it.  These  observations  led  to  a supposition, 
that  every  secretory  organ  is  originally  furnish- 
ed with  a humour  analogous  to  that  which  it  is 
afterwards  destined  to  separate  from  the  blood ; 
and  that  in  consequence  of  this  disposition,  the 
secretory  vessels  of  the  liver,  for  instance,  will 
only  admit  the  bilious  particles  of  the  blood, 
while  all  the  other  humours  will  be  excluded. 
This  system  is  an  ingenious  one,  but  the  dif- 
ficulties with  which  it  abounds  are  unanswer- 
able ; for  oil  and  water  are  immiscible  ; where- 
as the  blood,  as  it  is  circulated  through  the 
body,  appears  to  be  an  homogeneous  fluid* 


363 


Of  the  Thorax. 

Every  oil  will  pass  through  a paper  moistened 
only  with  one  kind  of  oil ) and  wine,  or  spirits 
mixed  with  water,  will  easily  be  filtered  through 
a paper  previously  soaked  in  water.  Upon 
the  same  principle,  all  our  humours,  though 
differing  in  their  other  properties,  yet  agree- 
ing in  that  of  being  perfectly  miscible  with 
each  other,  will  all  easily  pass  through  the 
same  filtre. — But  these  are  not  all  the  objec- 
tions to  this  system.  The  humours  which  are 
supposed  to  be  placed  in  the  secretory  vessels 
for  the  determination  of  similar  particles  of  the 
blood,  must  be  originally  separated  without 
any  analogous  fluid ; and  that  which  happens 
once,  may  as  easily  happen  always.  Again, 
it  sometimes  happens  from  a vicious  disposi- 
tion, that  humours  are  filtered  through  glands 
which  are  naturally  not  intended  to  afford 
them  a passage,  and  when  this  once  has  hap- 
pened, it  ought,  according  to  this  system,  to 
be  expected  always  to  do  so : whereas  this  is 
not  the  case ; and  we  are,  after  all,  naturally 
led  to  seek  for  the  cause  of  secretions  in  the 
solids.  It  does  not  seem  right  to  ascribe  it  to 
any  particular  figure  of  the  secretory  vessels  ; 
because  the  soft  texture  of  those  parts  does 
not  permit  them  to  preserve  any  constant 
shape,  and  our  fluids  seem  to  be  capable  of 
accommodating  themselves  to  every  kind  of 
figure.  Some  have  imputed  it  to  the  differ- 
ence of  diameter  in  the  orifices  of  the  differ- 
ent secretory  vessels.  To  this  doctrine  ob- 
jections have  likewise  been  raised ; and  it  has 
been  argued,  that  the  vessels  of  the  liver,  for 
instance,  would,  upon  this  principle,  afford  a 


364 


Of  the  Thorax. 


passage  not  only  to  the  bile,  but  to  all  the 
other  humours  of  less  consistence  with  it.  In 
reply  to  this  objection,  it  has  been  supposed, 
that  secondary  vessels  exist,  which  originate 
from  the  first,  and  permit  all  the  humours 
thinner  than  the  bile  to  pass  through  them. 

Each  of  these  hypotheses  is  probably  very 
remote  from  the  truth. 

i 


EXPLANATION  of  PLATE  XXVIII. 

This  plate  represents  the  Heart  in  situ,  all 
the  large  Arteries  and  Veins,  with  some  of  the 
Muscles,  £kc. 

Muscles,  &c. — Superior  Extremity.- — a, 
Masseter.  b,  Complexus.  c,  Digastricus.  d, 
Os  hyoides.  e,  Thyroid  gland,  f,  Levator 
scapulae,  g,  Cucullaris.  h h,  The  clavicles 
cut.  i,  The  deltoid  muscle,  k,  Biceps  flexor 
cubiti  cut.  1,  Caraco-brachialis.  m,  Triceps 
extensor  cubiti.  n,  The  heads  of  the  pronator 
teres,  flezor  carpi  radialis,  and  flexor  digito- 
rum  sublimis,  cut.  o,  The  flexor  carpi  ulna- 
ris,  cut  at  its  extremity,  p,  Plexor  digitorum 
profundus,  q,  Supinator  radii  longus,  cut  at 
its  extremity,  r,  Ligamentum  carpi  transver- 
sale.  s,  Extensores  carpi  radiales.  t,  Latis- 
simus  dorsi.  u,  Anterior  edge  of  the  serratus 
anticus  major,  v v,  The  inferior  part  of  the 
diaphragm,  w w,  Its  anterior  edge  cut.  x x, 
The  kidneys,  y,  Transversus  abdominis,  z, 
Os  ilium. 


* 


* 


Plate  XW  II! 


Of  the  Thorax. 


365 


Inferior  Extremity. — a , Psoas  magnus, 

Iliacus  internus.  c,  The  fleshy  origin  of  the 
tensor  vaginae  femoris.  d d , The  ossa  pubis 
cut  from  each  other,  e,  Musculus  pectineus 
cut  from  its  origin.  /,  Short  head  of  the  tri- 
ceps abductor  femoris  cut.  g , The  great  head 
of  the  triceps.  /z,  The  long  head  cut.  i,  Vas- 
tus internus.  Vastus  externus.  /,  Crure- 
us.  ra,  Gemellus.  w,  Soleus.  o,  Tibia,  p , 
Peronaeus  longus.  g,  Peronaeus  brevis,  r, 
Fibula. 

He  art  and  Blood-vessels.-— A,  The  heart, 
with  the  coronary  arteries  and  veins.  B,  The 
right  auricle  of  the  heart.  C,  The  aorta  ascen- 
dens.  D,  The  left  subclavian  artery.  E,  The 
left  carotid  artery.  F,  The  common  trunk 
which  sends  off  the  right  subclavian  and  right 
carotid  arteries.  G,  The  carotis  externa.  K, 
Arteria  facialis,  which  sends  off  the  coronary 
arteries  of  the  lips.  I,  Arteria  temporalis  pro- 
funda. K,  Aorta  descendens.  L L,  The 
iliac  arteries, — which  send  off  M M,  The  fe- 
moral or  crural  arteries.  N.  B.  The  other 
arteries  in  this  figure  have  the  same  distri- 
bution as  the  veins  of  the  same  name : — 
And  generally,  in  the  anatomical  plates,  the 
description  to  be  found  on  the  one  side,  points 
out  the  same  parts  in  the  other.  1,  The  fron- 
tal vein.  2,  The  facial  vein.  3,  Vena  tem- 
poralis profunda.  4,  Vena  occipitalis.  5, 
Vena  jugularis  externa.  6,  Vena  jugularis 
interna,  covering  the  arteria  carotis  commu- 
nis. 7.  The  vascular  arch  on  the  palm  of  the 
hand,  which  is  formed  by,  8,  The  radial  ar- 
tery and  vein,  and,  9,  The  ulnar  artery  and 


366 


Of  the  Brain  and  Nerves. 


vein.  10  10,  Cephalic  vein.  11,  Basilic  vein, 
that  on  the  right  side  cut.  12,  Median  vein. 
13,  The  humeral  vein,  which,  with  the  me- 
dian, covers  the  humeral  artery.  14  14,  The 
external  thoracic  or  mammary  arteries  and 
veins.  15,  The  axillary  vein,  covering  the 
artery.  16  16,  The  subclavian  veins,  which, 
with  (6  6)  the  jugulars,  form,  17,  The  vena 
cava  superior.  18,  The  cutaneous  arch  of 
veins  on  the  fore  part  of  the  foot.  19,  The 
vena  tibialis  antica,  covering  the  artery.  20, 
The  vena  profunda  femoris,  covering  the  ar- 
tery. 21,  The  upper  part  of  the  vena  saphena 
major.  22,  The  femoral  vein.  23  23,  The 
iliac  veins.  24  24,  Vena  cava  inferior.  25  25, 
The  renal  veins  covering  the  arteries.  26  26* 
The  diaphragmatic  veins. 


PART  V.  OF  THE  BRAIN  AND 
NERVES. 


Sect.  I.  Of  the  Brain  and  its  Integuments. 
HE  bones  of  the  cranium  were  described 


in  the  osteological  part  of  this  work,  as 
inclosing  the  brain,  and  defending  it  from  ex- 
ternal injury  : but  they  are  not  its  only  pro- 
tection ; for  when  we  make  an  horizontal  sec- 
tion through  these  bones,  we  find  this  mass 


367 


Of  the  Brain  and  Nerves. 

every  where  surrounded  by  two  membranes,* 
the  dura  and  pia  mater. — The  first  of  these 
lines  the  interior  surface  of  the  cranium,  to 
which  it  every  where  adheres  strongly,!  but 
more  particularly  at  the  sutures,  and  at  the 
many  foramina  through  which  vessels  pass 
between  it  and  the  pericranium.  The  dura 
mater  % is  perfectly  smooth  and  inelastic,  and 
its  inner  surface  is  constantly  bedewed  with  a 
fine  pellucid  fluid,  which  every  where  sepa- 
rates it  from  the  pia  mater.  The  dura  mater 
sends  off  several  considerable  processes,  which 
divide  the  brain  into  separate  portions,  and 
prevent  them  from  compressing  each  other. 
Of  these  processes  there  is  one  superior  and 
longitudinal,  called  the  falx  or  falciform  pro - 
cess , from  its  resemblance  to  a scythe.  It 
arises  from  the  spine  of  the  os  frontis,  near 
the  crista  galli,  and  extending  along  in  the 
direction  of  the  sagittal  suture,  to  beyond  the 
lambdoidal  suture,  divides  the  brain  into  two 
hemispheres.  A little  below  the  lambdoidal 


* The  Greeks  called  these  membranes  meninges  : but  the  Ara- 
bians,  supposing  them  to  be  the  source  of  all  the  other  mem- 
branes  of  the  body,  afterwards  gave  them  the  names  of  dura  and 
pia  mater  ; by  which  they  are  now  usually  distinguished. 

! In  young  subjects  this  adhesion  is  greater  than  in  adults  ; 
but  even  then,  in  the  healthy  subject,  it  is  no  where  easily  sepa- 
rable, without  breaking  through  some  of  the  minute  vessels  by 
means  of  which  it  is  attached  to  the  bone. 

! This  membrane  is  commonly  described  as  consisting  of  two 
laminae ; of  which  the  external  one  is  supposed  to  perform  the  of- 
fice of  periosteum  internum  to  the  cranium,  -while  the  internal 
one  forms  the  folds  and  processes  of  the  dura  mater.  In  the  na- 
tural state,  however,  no  such  separation  is  apparent.;  like  other 
membranes,  we  may  indeed  divide  it,  not  into  two  only,  buc 
many  laminae ; but  this  division  is  artificial,  and  depends  on  the 
dexterity  of  the  anatomist. 


368  Of  the  Brain  and  Nerves. 

suture,  it  divides  into  two  broad  wings  or  ex- 
pansions called  the  transverse  or  lateral  process- 
es, which  prevents  the  lobes  of  the  cerebrum 
from  pressing  on  the  cerebellum.  Besides 
these  there  is  a fourth,  which  is  situated  under 
the  transverse  processes,  and  being  continued 
to  the  spine  of  the  occiput,  divides  the  cere- 
bellum into  two  lobes. 

The  blood,  after  being  distributed  through 
the  cavity  of  the  cranium  by  means  of  the  ar- 
teries, is  returned,  as  in  the  other  parts  of  the 
body,  by  veins  which  all  pass  on  to  certain 
channels,  situated  behind  these  several  pro- 
cesses. 

These  canals  or  sinuses  communicate  with 
each  other,  and  empty  themselves  into  the  in- 
ternal jugular  veins,  which  convey  the  blood 
into  the  vena  cava.  They  are  in  fact  triangu- 
lar veins,  running  through  the  substance  of  the 
dura  mater,  and,  like  the  processes,  are  dis- 
tinguished into  longitudinal  and  lateral;  and 
where  these  three  meet,  and  where  the  fourth 
process  passes  off,  we  observe  a fourth  sinus, 
which  is  called  torcular  ; Herophilus,  who  first 
described  it,  having  supposed  that  the  blood  at 
the  union  of  these  two  veins,  is,  as  it  were,  in 
a press. 

Besides  these  four  canals,  which  were 
known  to  the  ancients,  modern  anatomists  enu- 
merate many  others,  by  giving  the  appellation 
of  sinuses  to  other  veins  of  the  dura  mater, 
which  for  the  most  part  empty  themselves  into 
some  of  those  we  have  just  now  described. 
There  are  the  inferior  longitudinal  sinus,  the 
superior  and  inferior  petrous  sinuses,  the  ca- 


369 


Of  the  Brain  and  Nerves. 

'vernous  sinuses,  the  circular  sinus,  and  the 
anterior  and  posterior  occipital  sinuses. 

These  sinuses  or  veins,  by  being  conveyed 
through  a thick  dense  membrane,  firmly  sus- 
pended, as  the  dura  mater  is,  within  the  cra- 
nium, are  less  liable  to  rupture  ; at  the  same 
time  they  are  well  supported,  and  by  running 
every  where  along  the  inner  surface  of  the 
bones,  they  are  prevented  from  pressing  on  the 
substance  of  the  brain.  To  prevent  too  great 
a dilatation  of  them,  we  find  filaments  (called 
chorda  JBillisii , from  their  having  been  first 
noticed  b\  Willis)  stretched  across  their  cavi- 
ties ; and  the  oblique  manner  in  which  the 
veins  from  the  brain  run  through  the  substance 
of  the  brain  into  these  channels,  serves  the 
purpose  of  a valve,  which  prevents  the  blood 
from  turning  back  into  the  smaller  and  weaker 
vessels  of  the  brain. 

The  pia  mater  is  a much  softer  and  finer 
membrane  than  the  dura  mater ; being  exceed- 
ingly delicate,  transparent,  and  vascular.  It  in- 
vests every  part  of  the  brain,  and  sends  off  an 
infinite  number  of  elongations,  which  insinu- 
ate themselves  between  the  convolutions,  and 
even  into  the  substance  of  the  brain.  Tins 
membrane  is  composed  of  two  laminae  ; of  which 
the  exterior  one  is  named  tunica  arachnoiclea , 
from  its  thinness,  which  is  equal  to  that  of  a 
spider’s  web.  These  two  laminae  are  intimate- 
ly adherent  to  each  other  at  the  upper  part  of 
the  brain,  but  are  easily  separable  at  the  basis 
of  the  brain,  and  through  the  whole  length  of 
the  medulla  spinalis.  The  external  layer,  or 
tunica  araehnoidea,  appears  to  be  spread  uni- 

3 A 


370 


Of  the  Brain  and  Nerves. 


formly  over  the  surface  of  the  brain,  but  with- 
out entering  into  its  furrows  as  the  inner  layer 
does  ; the  latter  being  found  to  insinuate  itself 
between  the  convolutions,  and  even  into  the 
interior  cavities  of  the  brain.  The  blood-ves- 
sels of  the  brain  are  distributed  through  it  in 
their  way  to  that  organ,  and  are  therefore  di- 
vided into  very  minute  ramifications,  before 
they  penetrate  the  substance  of  the  brain. 

There  are  several  parts  included  under  the 
general  denomination  of  brain.  One  of  these, 
which  is  of  the  softest  consistence,  and  fills 
the  greatest  part  of  the  cavity  of  the  cranium, 
is  the  cerebrum , or  brain  properly  so  called. 
Another  portion,  which  is  seated  in  the  infe- 
rior and  posterior  part  of  the  head,  is  the  cere- 
bellum ; and  a third,  which  derives  its  origin 
from  both  these,  is  the  medulla  oblongata. 

The  cerebrum  is  a medullary  mass  of  a mo- 
derate consistence,  filling  up  exactly  all  the 


upper  part  of  the  cavity  of  the  cranium,  and 
divided  into  two  hemispheres  by  the  falx  of 
the  dura  mater.  Each  of  these  hemispheres 
is  usually  distinguished  into  an  interior , a mid- 
dle, and  a posterior  lobe.  The  first  of  these  is 
lodged  on  the  orbital  processes  of  the  os  fron- 
tis  : the  middle  lobes  he  on  the  middle  fosste  of 
the  basis  of  the  cranium,  and  the  posterior 
lobes  are  placed  on  the  transverse  septum  of 
the  os  occipitis,  immediately  over  the  cerebel- 
lum, from  which  they  are  separated  by  the  la- 
teral processes  of  the  dura  mater.  These  two 
portions  afford  no  distinguishing  mark  of  se- 
paration ; and  on  this  account  Iialler,  and  many 
other  modern  anatomists,  omit  the  distinction 


Of  the  Brain  ancl  Nerves.  371 

ef  middle  lobe,  and  speak  only  of  the  anterior 
and  posterior  lobes  of  the  brain. 

The  cerebrum  appears  to  be  composed  of 
two  distinct  substances.  Of  these,  the  exte- 
rior one,  which  is  of  a greyish  or  ash-colour, 
is  called  the  cortex , and  is  somewhat  softer 
than  the  other,  which  is  very  white,  and  is  call- 
ed medulla  or  substantia  alba. 

After  having  removed  the  falx,  and  separat- 
ed the  two  hemispheres  from  each  other,  we 
perceive  a white  convex  body,  the  corpus  cal- 
losum, which  is  a portion  of  the  medullary 
substance,  uniting  the  two  hemispheres  to 
each  other,  and  not  invested  by  the  cortex. 
By  making  an  horizontal  incision  in  the  brain, 
on  a level  with  this  corpus  callosum,  we  dis- 
cover two  oblong  cavities,  named  the  anterior 
or  lateral  ventricles , one  in  each  hemisphere. 
These  two  ventricles,  which  communicate  with 
each  other  by  a hole  immediately  under  the 
plexus  choroides,  are  separated  laterally  by  a 
very  fine  medullary  partition,  called  septum 
lucidum , from  its  thinness  and  transparency. 
The  lower  edge  of  this  septum  is  fixed  to  the 
fornix,  which  is  a kind  of  medullary  arch  (as 
its  name  implies)  situated  under  the  corpus 
callosum,  and  nearly  of  a triangular  shape. 
Anteriorly  the  fornix  sends  off  two  medullary 
chords,  called  its  anterior  crura;  which  seem 
to  be  united  to  each  other  by  a portion  of  me- 
dullary substance,  named  commissura  anterior 
cerebri.  These  crura  diverging  from  one  ano- 
ther, are  lost  at  the  outer  side  of  the  lower 
and  fore-part  of  the  third  ventricle.  Posteri- 
orly the  fornix  is  formed  into  two  other  crura. 


"372  Of  the  Brain  and  Nerves. 

which  unite  with  two  medullary  protuberances 
called  pedes  hippocampi , and  sometimes  cornua 
ammonis , t .at  extend  along  the  back  part  of 
the  lateral  ventricles.  The  concave  edge  of 
the  pedes  hippocampi  is  covered  by  a medul- 
lary lamina,  called  corpus  fmbriatum. 

Neither  the  edges  of  the  fornix,  nor  its  pos- 
terior crura,  can  be  well  distinguished,  till  we 
have  removed  the  plexus  choroides.  This  is 
a production  of  the  pia  mater,  which  is  spread 
over  the  lateral  ventricles.  Its  loose  edges 
are  collected,  so  as  to  appear  like  a vascular 
band  on  each  side. 

When  we  have  removed  this  plexus,  we  dis- 
cover several  other  protuberances  included  in 
the  lateral  ventricles.  These  are  the  corpora 
striata,  the  thalami  nervorum  opticorum,  the 
tubercula  quadrumgemina,  and  the  pineal 
gland. 

The  corpora  striata  are  two  curved  oblong 
eminences,  that  extend  along  the  anterior  part 
of  the  lateral  ventricles.  They  derive  their 
name  from  their  striated  appearance,  which  is 
owing  to  an  intermixture  of  the  cortical  and 
medullary  substances  of  the  brain.  The  thala- 
mi nervorum  opticorum , are  so  called,  because 
the  optic  nerves  arise  chiefly  from  them,  and 
they  are  likewise  composed  both  of  the  cortex 
and  medulla.  They  are  separated  from  the 
corpora  striata  only  by  a kind  of  medullary 
chord,  the  geminum  centrum  semi-circulare. 
The  thalami  are  nearly  of  an  oval  shape,  and 
are  situated  at  the  bottom  of  the  upper  cavity 
of  the  lateral  ventricles.  They  are  closely 


373 


Of  the  Brain  and  Nerves. 

united,  and  at  their  convex  part  seem  to  be- 
come one  body. 

Anteriorly,  in  the  space  between  the  thala- 
mi,  we  observe  an  orifice  by  which  the  lateral 
ventricles  communicate,  and  another  leads 
down  from  this,  under  the  different  appella- 
tions of  foramen  commune  anterius , vulva  iter 
ad  infundibulum , but  more  properly  iter  ad  ter- 
tium  ventriculum and  the  separation  of  the, 
thalami  from  each  other  posteriorly,  forms 
another  opening  or  interstice  called  anus.  This 
has  been  supposed  to  communicate  with  the 
third  ventricle  ; but  it  does  not,  the  bottom  of 
it  being  shut  up  by  the  pia  mater.  The  back 
part  of  the  anus  is  formed  by  a kind  of  medul- 
lary band,  which  connects  the  thalami  to  each 
other,  and  is  called  commissura  posterior  ce- 
rebri. 

Behind  the  thalami  and  commissura  poste- 
rior, we  observe  a small,  soft,  greyish,  and 
oval  body,  about  the  size  of  a pea.  This  is 
the  glandula  pinealis  ; it  is  described  by  Galen, 
under  the  name  of  conarion , and  has  been  ren- 
dered famous  by  Descartes,  who  supposed  it 
to  be  the  seat  of  the  soul.  Galen  seems  for- 
merly to  have  entertained  the  same  opinion. 
Some  modern  writers  have,  with  as  little  rea- 
son, imagined  that  the  soul  is  placed  in  the 
corpus  callosum. 

The  pineal  gland  rests  upon  four  remarka- 
ble eminences,  disposed  in  pairs,  and  seated 
immediately  below  it.  These  tubercles,  which 
by  the  ancients  were  called  testes  and  nates , 
have,  since  the  time  of  Winslow,  been  more 
commonly  named  tuber cula  quadrugemina. 


374  Of  the  Brain  and  Nerves. 

Under  the  thalami  we  observe  another  ca- 
vity, the  third  ventricle,  which  terminates  an- 
tenorly  in  a small  medullary  canal,  the  infun- 
dibulum, that  leads  to  the  glandula  pituitaria. 

It  has  been  doubted,  whether  the  infundi- 
bulum is  really  hollow ; but  some  late  experi- 
ments on  this  part  of  the  brain*  by  Professor 
Murray  of  Upsal,  clearly  prove  it  to  be  a me- 
dullary canal,  surrounded  by  both  laminae  of 
the  pia  mater.  After  freezing  the  brain,  this 
channel  was  found  filled  with  ice;  and  de' 
Haen  tells  f us,  he  found  it  dilated,  and  filled 
with  a calcareous  matter.^ 

The  soft  spongy  body  in  which  the  infundi- 
bulum terminates,  was  by  the  ancients  sup- 
posed to  be  of  a glandular  structure,  and  des- 
tined to  filter  the  serosity  of  the  brain.  Spi- 
gelius  pretended  to  have  discovered  its  excre- 
tory duct,  but  it  seems  . certain  that  no  such 
duct  exists.  It  is  of  an  oblong  shape,  com- 
posed, as  it  were,  of  two  lobes.  In  ruminant 
Animals  it  is  much  larger  than  in  man. 

From  the  posterior  part  of  the  third  ventri- 
cle, we  see  a small  groove  or  channel,  de- 
scending obliquely  backwards.  This  channel, 
which  is  called  the  aqueduct  of  Sylvius , though 
It  was  known  to  the  ancients,  opens  into  ano- 
ther cavity  of  the  brain,  placed  between  the 
cerebellum  and  medulla  oblongata,  and  called 
the  fourth  ventricle. 

* Disp.  de  Infundibulo  Cerebri. 

f Ratio  Med.  tom.  vi.  p.  271. 

I The  under  part  of  it,  however,  appears  to  be  impervious ; 
at  least  no  injection  that  can  be  depended  on  has  been  made  to 
pass  from  it  into  the  glandula  pituitaria  without  laceration  of 
parts. 


375 


Of  the  Brain  and  Nerves. 

The  cerebellum , which  is  divided  into  two 
lobes,  is  commonly  supposed  to  be  of  a firmer 
texture  than  the  cerebrum ; but  the  truth  is, 
that  in  the  greater  number  of  subjects,  there 
Appears  to  be  no  sensible  difference  in  the  con- 
sistence of  these  two  parts.  It  has  more  of  the 
cortical  than  of  the  medullary  substance  in  its 
composition. 

The  furrow  that  divides  the  two  lobes  of 
the  cerebellum  leads  anteriorly  to  a process, 
composed  of  medullary  and  cortical  substan- 
ces, covered  by  the  pia  mater ; and  which, 
from  its  being  divided  into  numerous  furrows, 
resembling  the  rings  of  the  earth-worm,  is 
named  processus  vermiformis.  This  process 
forms  a kind  of  ring  in  its  course  between  the 
lobes. 

The  surface  of  the  cerebellum  does  not  af- 
ford those  circumvolutions  which  appear  in  the 
cerebrum;  but  instead  of  these,  we  observe  a 
great  number  of  minute  furrows,  running  pa- 
rallel to  each  other,  and  nearly  in  a transverse 
direction.  The  pia  mater  insinuates  itself  into 
these  furrows. 

When  we  cut  into  the  substance  of  the  cere- 
bellum, from  above  downwards,  we  find  the 
medullary  part  running  in  a kind  of  ramifying 
course,  and  exhibiting  an  appearance  that  has 
gotten  the  name  of  arbor  vita.  These  ramifi- 
cations unite  to  form  a medullary  trunk ; the 
middle,  anterior,  and  most  considerable  part 
of  which  forms  two  processes,  the  crura  cere- 
helli,  which  unite  with  the  crura  cerebri,  to 
form  the  medulla  oblongata.  The  last  furnish- 
es two  other  processes,  which  lose  themselves 


376  Of  the  Brain  and  Nerves. 

under  the  nates,  and  thus  unite  the  lobes  of 
the  cerebellum  to  the  posterior  part  of  the  ce- 
. rebrum.  Under  the  nates  we  observe  a trans- 
verse medullary  line,  or  linea  alba,  running 
from  one  of  these  processes  to  the  other  ; and 
between  them  we  find  a very  thin  medullary 
damma,  covered  with  the  pia  mater,  which 
the  generality  of  anatomists  have  (though 
seemingly  without  reason)  considered  as  a 
valve  formed  for  closing  the  communication 
between  the  fourth  ventricle  and  the  aquaeduc- 
-tus  Sylvii.  Vieussens  named  it  valvula  ma- 
jor cerebri. 

The  medulla  oblongata  is  situated  in  the  mid- 
dle, lower,  and  posterior  part  of  the  cranium, 
and  may  be  considered  as  a production  or  con- 
tinuation of  the  whole  medullary  substance  of 
the  cerebrum  and  cerebellum,  being  formed 
by  the  union  of  two  considerable  medullary 
processes  of  the  cerebrum,  called  crura  cerebri , 
with  two  other  smaller  ones  from  the  cerebel- 
lum, which  were  just  now  spoken  of  under 
the  name  of  crura  cerebelli. 

The  crura  cerebri  arise  from  the  middle  and 
lower  part  of  each  hemisphere.  They  are  se- 
parated from  each  other  at  their  origin,  but  are 
united  below,  where  they  terminate  in  a mid- 
dle protuberance,  the  pons  Varolii , so  called, 
because  Varolius  compared  it  to  a bridge. 
This  name,  however,  can  convey  no  idea  of  its 
real  appearance.  It  is,  in  fact,  nothing  more 
than  a medullary  protuberance,  nearly  of  a se- 
nt -spherical  shape,  which  unites  the  crura  ce- 
rebri to  those  of  tne  cerebellum. 


377 


Of  the  Brain  and  Nerves. 

Between  the  crura  cerebri,  and  near  the  an- 
terior edge  of  the  pons  Varolii,  are  two  tuber- 
cles, composed  externally  of  medullary,  and 
internally  of  cineritious,  substance,  to  which 
Eustachius  first  gave  the  name  of  eminently 
mamillares. 

Along  the  middle  of  the  posterior  surface 
of  the  medulla  oblongata,  where  it  forms  the 
anterior  part  of  the  fourth  ventricle,  we  observe 
a kind  of  furrow  which  runs  downwards  and 
terminates  in  a point.  About  an  inch  above 
the  lower  extremity  of  this  fissure,  several  me- 
dullary filaments  are  to  be  seen  running  up- 
wards it  on  each  side  in  an  oblique  direction, 
so  as  to  give  it  the  appearance  of  a writing- 
pen  ; hence  it  is  called  calamus  scriptorius. 

From  the  posterior  part  of  the  pons  Varolii, 
the  medulla  oblongata  descends  obliquely  back- 
wards ; at  its  fore-part,  immediately  behind 
the  pons  Varolii,  we  observe  two  pair  of  emi- 
nences, which  were  described  by  Eustachi- 
us, but  received  no  particular  appellation  till 
the  time  of  Vieussens,  who  gave  them  the 
names  of  corpora  olivaria  and  corpora  pyrami- 
dalia.  The  former  are  the  outermost,  being 
placed  one  on  each  side.  They  are  nearly  of 
an  oval  shape,  and  are  composed  of  medulla, 
with  streaks  of  cortical  substance.  Between 
these  are  the  corpora  pyramidalia,  each  of 
which  terminates  in  a point.  In  the  human 
subject  these  four  eminences  are  sometimes 
not  easily  distinguished. 

The  medulla  spinalis  or  spinal  marrow , 
which  is  the  name  given  to  the  medullary 
chord  that  is  extended  down  the  vertebral  ca- 

3 B 


37B  Of  the  Brain  and  Nerves . 

nal,  from  the  great  foramen  of  the  occipitai 
bone  to  the  bottom  of  the  last  lumbar  vertebra, 
is  a continuation  of  the  medulla  oblongata.  Like 
the  other  parts  of  the  brain,  it  is  invested  by 
the  dura  and  pia  mater.  The  first  of  these,  in 
its  passage  out  of  the  cranium,  adheres  to  the 
foramen  of  the  os  occipitis.  Its  connection  with 
the  ligamentary  substance  that  lines  the  cavity 
of  the  spine,  is  only  by  means  of  cellular  mem- 
brane ; but  between  the  several  vertebrae.,  where 
the  nerves  pass  out  of  the  spine,  it  sends  off 
prolongations,  which  adhere  strongly  to  the 
vertebral  ligaments.  Here,  as  in  the  cranium, 
the  dura  mater  has  its  sinuses  or  large  veins. 
These  are  two  in  number,  and  are  seen  run- 
ning on  each  side  of  the  medullary  column, 
from  the  foramen  magnum  of  the  os  occipitis 
to  the  lower  part  of  the  os  sacrum.  They 
communicate  together  by  ramifying  branches 
at  each  vertebra,  and  terminate  in  the  verte- 
bral, intercostal,  and  sacral  veins. 

The  pia  mater  is  connected  with  the  dura 
mater  by  means  of  a thin  transparent  sub- 
stance which  from  its  indentations  between 
the  spinal  nerves  has  obtained  the  name  of 
ligamentum  denticulatum.  It  is  somewhat  firm- 
er than  the  tunica  arachnoidea,  but  in  other  re- 
spects resembles  that  membrane.  Its  use  is 
to  support  the  spinal  marrow,  that  it  may  not 
affect  the  medulla  oblongata  by  its  weight. 

The  spinal  marrow  itself  is  externally  of  a 
white  colour  ; but  upon  cutting  into  it  we  find 
its  middle-part  composed  of  a darker  coloured 
mass,  resembling  the  cortex  of  the  brain.  When 
the  marrow  has  reached  the  first  lumbar  yer- 


Of  the  Brain  and  Nerves.  379 

tehra,  it  becomes  extremely  narrow,  and  at 
length  terminates  in  an  oblong  protuberance  ; 
from  the  extremity  of  which  the  pia  mater 
sends  off  a prolongation  or  ligament,  resem- 
bling a nerve,  that  perforates  the  dura  mater, 
and  is  fixed  to  the  os  coccygis. 

The  medulla  spinalis  gives  rise  to  30  or  3 1 
pair  of  nerves,  but  they  are  not  ail  of  the  same 
size,  nor  do  they  all  run  in  the  same  direc- 
tion. The  upper  ones  are  thinner  than  the 
rest,  and  are  placed  almost  transversely : as 
we  descend  we  find  them  running  more  and 
more  obliquely  downwards,  till  at  length  their 
course  is  almost  perpendicular,  so  that  the  low- 
ermost nerves  exhibit  an  appearance  that  is 
called  cauda  equina,  from  its  resemblance  to  a 
horse’s  tail. 

The  arteries  that  ramify  through  the  differ- 
ent parts  of  the  brain,  are  derived  from  the 
internal  carotid  and  from  the  vertebral  arteries. 
The  medulla  spinalis  is  supplied  by  the  ante- 
rior and  posterior  spinal  arteries,  and  likewise 
receives  branches,  from  the  cervical,  the  infe- 
rior and  superior  intercostal,  the  lumbar,  and 
the  sacral  arteries. 


Sect.  II.  Of  the  Nerves. 

The  nerves  are  medullary  chords,  differing 
from  each  other  in  size,  colour,  and  consist- 
ence, and  deriving  their  origin  from  the  me- 
dulla oblongata  and  medulla  spinalis.  There 
are  39,  andsometimes  40,  pair  of  these  nerves; 


38  0 


Of  the  Brain  and  Nerves . 


nine*  of  which  originate  from  the  medulla 
oblongata,  and  30  or  31  from  the  medulla  spi- 
nalis. They  appear  to  be  perfectly  inelastic, 
and  likewise  to  possess  no  irritability.  If  we 
irritate  muscular  fibres,  they  immediately  con- 
tract ; but  nothing  of  this  sort  happens  if  we 
irritate  a nerve.  They  carry  with  them  a co- 
vering from  the  pia  mater  ; but  derive  no  tu- 
nic from  the  dura  mater,  as  hath  been  gene- 
rally, though  erroneously,  supposed,  ever  since 
the  time  of  Galen, f the  outer  covering  of  the 
nerves  being  in  fact  nothing  more  than  the  cel- 
lular membrane.  This  covering  is  very  thick, 
where  the  nerve  is  exposed  to  the  action  of 
muscles  ; but  where  it  runs  through  a bony  ca- 
nal, or  is  secure  from  pressure,  the  cellular 
tunic  is  extremely  thin,  or  altogether  wanting. 
We  have  instances  of  this  in  the  portio  mollis 
of  the  auditory  nerve,  and  in  the  nerves  of  the 
heart. 

By  elevating,  carefully  and  gently,  the  brain 
from  the  basis  of  the  cranium,  we  find  the  first 
nine  pair  arising  in  the  following  order:  1, 

The  nervi  olfactorii,  distributed  through  the 
pituitary  membrane,  which  constitutes  the  or- 
gan of  smell.  2.  The  optici,  which  go  to  the 

* It  has  been  usual  to  describe  the  ten  pair  of  nerves  as  aris- 
ing from  the  medulla  oblongata  ; but  as  the  tenth  pair  arise  in 
the  fame  manner  as  the  other  spinal  nerves,  Santorini,  Heister, 
Haller,  and  others,  seem  very  properly  to  have  classed  them 
among  the  nerves  of  the  spine. 

-}•  Baron  Haller  and  Professor  Zinn  seem  to  have  been  the 
first  who  demonstrated,  that  the  dura  mater  is  reflected  upon 
and  adheres  to  the  periosteum  at  the  edges  of  the  foramina  that 
afford  a passage  to  the  nerves  out  of  the  cranium,  and  vertebral 
•canal,  or  is  soon  lost  in  the  cellular  substance, 


Of  the  Brain  and  Nerves.  381 

eyes,  where  they  receive  the  impressions  of 
visible  objects.  3.  The  oculorum  motores,  so 
called  because  they  are  distributed  to  the  mus- 
cles of  the  eye.  4.  The  pathetici,  distributed 
to  the  superior  oblique  muscles  of  the  eye,  the 
motion  of  which  is  expressive  of  certain  passions 
of  the  soul.  5.  The  nerves  of  this  pair  soon 
divide  into  three  principal  branches,  and  each 
of  these  has  a different  name.  Its  upper  di- 
vision is  the  ophthalmicus,  which  is  distribut- 
ed to  various  parts  of  the  eyes,  eye-lids,  fore- 
head, nose,  and  integuments  of  the  face.  The 
second  is  called  the  maxillaris  superior , and 
the  third  maxillaris  inferior  ; both  which  names 
allude  to  their  distribution.  6.  The  abducto- 
res  ; each  of  these  nerves  is  distributed  to  the 
abductor  muscle  of  the  eye,  so  called,  because 
it  helps  to  draw  the  globe  of  the  eye  from  the 
nose.  7.  The  auditorii,*  which  are  distribut- 
ed through  the  organs  of  hearing.  8.  The 
par  vagum,  which  derives  its  name  from  the 
great  number  of  parts  to  which  it  gives  branch- 
es both  in  the  thorax  and  abdomen.  9.  The 
linguales,  or  hypo-glossi,  which  are  distribut- 
ed to  the  tongue,  and  appear  to  contribute  both 
to  the  organ  of  taste  and  to  the  motions  of  the 
tongue. f 

* This  pair,  soon  after  its  entrance  into  the  meatus  auditorius 
internus,  separates  into  two  branches.  One  of  these  is  of  a very- 
soft  and  pulpy  consistence,  it  is  called  the  portio  mollis  of  the  se- 
venth pair,  and  is  spread  over  the  inner  part  of  the  ear.  The 
other  passes  out  through  the  aqueduct  of  Fallopius  in  a firm 
chord,  which  is  distinguished  as  the  portio  dura,  and  is  distribut- 
ed to  the  external  ear  and  other  parts  of  the  neck  and  face. 

f Heister  has  summed  up  the  ufes  of  these  nine  pair  of 
nerves  in  the  two  following  Latin  verses  : 


382 


Of  the  Brain  and  Nerves . 


It  has  already  been  observed,  that  the  spi- 
nal marrow  sends  off  30  or  31  pair  of  nerves  ; 
these  are  chiefly  distributed  to  the  exterior  parts 
of  the  trunk  and  to  the  extremities.  They  are 
commonly  distinguished  into  the  cervical , dorsals 
lumbar , and  sacral  nerves.  The  cervical,  which 
pass  out  from  between  the  several  vertebrae 
of  the  neck  are  eight'*'  in  number  ; the  dorsal, 
twelve  ; the  lumbar,  five ; and  the  sacral,  five 
or  six  ; the  number  of  the  latter  depending  on 
the  number  of  holes  in  the  os  sacrum.  Each 
spinal  nerve  at  its  origin  is  composed  of  two 
fasciculi  of  medullary  fibres.  One  of  these 
fasciculi  arises  from  the  anterior,  and  the  other 
from  the  posterior,  surface  of  the  medulla. 
These  fasciculi  are  separated  by  the  ligamen- 
tum  denticulatum  ; after  which  we  find  them 
contiguous  to  one  another.  They  then  perfo- 
rate the  dura  mater,  and  unite  to  form  a con- 
siderable knot  or  ganglion.  Each  of  these 

“ O'faciens,  cernens,  oculosque  movnis,  paliensque, 

“ Gas  tans,  abducens,  audiensque,  magans  que,  loquinsquc .” 

* Besides  these,  there  is  another  pair  called  accessorii , which 
ari-es  from  the  medulla  spinalis  at  its  beginning;  and  ascending 
through  die  great  foramen  of  the  os  occipitis  into  the  cranium, 
passes  out  again  close  to  the  eighth  pair,  with  which,  however, 
it  does  not  unite  ; and  it  is  afterwards  distributed  chiefly  to  the 
muscles  of  the  neck,  back,  and  scapula.  In  this  course  it  sends 
off  filaments  to  different  parts,  and  likewise  communicates  with 
several  other  nerves.  Physiologists  are  at  a loss  how  to  account 
for  the  singular  origin  and  couise  of  these  nervi  accessorii.  The 
ancients  considered  them  as  branches  of  the  eighth  pair,  distri- 
buted to  muscles  of  the  scapula  : Willis  likewise  considered  them 
as  appendages  to  that  pair,  and  on  that  account  named  them  ac - 
cessorii.  They  are  sometimes  called  the  spinal  pair  ; but  as  this 
latter  name  is  applicable  to  all  the  nerves  of  the  spine  indiscrimi- 
nately, it  seems  better  to  adopt  that  given  by  Willis. 


383 


Of  the  Brain  and  Nerves. 

ganglions  sends  off  two  branches  ; one  ante- 
rior, and  the  other  posterior.  The  anterior 
branches  communicate  with  each  other  at  their 
coming  out  of  the  spine,  and  likewise  send  off 
one,  and  sometimes  more  branches,  to  assist 
in  the  formation  of  the  intercostal  nerve. 

The  knots  or  ganglions  of  the  nerves  just 
now  spoken  of,  are  not  only  to  be  met  with  at 
their  exit  from  the  spine,  but  likewise  in  vari- 
ous parts  of  the  body.  They  occur  in  the 
nerves  of  the  medulla  oblongata,  as  well  as  in 
those  of  the  spine.  They  are  not  the  effects 
of  disease,  but  are  to  be  met  with  in  the  same 
parts  of  the  same  nerves,  both  in  the  foetus 
and  adult.  They  are  commonly  of  an  oblong 
shape,  and  of  a greyish  colour,  somewhat  in- 
clined to  red,  which  is  perhaps  owing  to  their 
being  extremely  vascular.  Internally  we  are 
able  to  distinguish  something  like  an  intermix- 
ture of  the  nervous  filaments. 

Some  writers  have  considered  them  as  so 
many  little  brains  ; Lancisi  fancied  he  had  dis- 
covered muscular  fibres  in  them,  but  they  are 
certainly  not  of  an  irritable  nature.  A late 
writer,  Dr.  Johnstone,*  imagines  they  are  in- 
tended to  deprive  us  of  the  power  of  the  will 
over  certain  parts,  as  the  heart,  for  instance ; 
but  if  this  hypothesis  were  well  founded,  we 
should  meet  with  them  only  in  the  nerves  lead- 
ing to  involuntary  muscles  ; whereas  it  is  cer- 
tain, that  the  voluntary  muscles  receive  their 
nerves  through  ganglions.  Doctor  Monro, 
from  observing  the  accurate  intermixture  of  the 


Essay  on  the  Use  of  the  Ganglions  of  the  Nerves. 


384  Of  the  Brain  and  Nerves. 

minute  nerves  which  compose  them,  considers 
them  as  new  sources  of  nervous  energy. f 

The  nerves,  like  the  blood-vessels,  in  their 
course  through  the  body,  communicate  with 
each  other  ; and  each  of  these  communications 
constitutes  what  is  called  a plexus , from  whence 
branches  are  again  detached  to  different  parts 
of  the  body.  Some  of  these  are  constant  and 
considerable  enough  to  be  distinguished  by 
particular  names,  as  the  semilunar  plexus ; the 
pulmonary  plexus;  the  hepatic , the  cardiac,  &c. 

It  would  be  foreign  to  the  purpose  of  this 
work,  to  follow  the  nerves  through  all  their 
distributions  ; but  it  may  be  remembered,  that  in 
describing  the  different  viscera,  mention  was 
made  of  the  nerves  distributed  to  them.  There 
is  one  pair,  however,  called  the  intercostal , or 
great  sympathetic  nerve , which  seems  to  require 
particular  notice,  because  it  has  an  almost 
universal  connection  and  correspondence  with 
all  the  other  nerves  of  the  body.  Authors  are 
not  perfectly  agreed  about  the  origin  of  the 
intercostal  ; but  it  may  perhaps  not  improperly 
be  described,  as  beginning  from  filaments  of  the 
fifth  and  sixth  pair ; it  then  passes  out  of  the 
cranium,  through  the  bony  canal  of  the  carotid, 
from  whence  it  descends  laterally  close  to  the 
bodies  of  the  vertebrae,  and  receives  branches 
from  almost  all  the  vertebral  nerves  ; forming 
almost  as  many  ganglions  in  its  course  through 
the  thorax  and  abdomen.  It  sends  off  an 
infinite  number  of  branches  to  the  viscera  in 


f Observations  on  the  Nervous  System. 


Of  the  Brain  and  Nerves. 


385 


those  cavities,  and  forms  several  plexuses  with 
tiie  branches  of  the  eighth  pair  or  par  vagum. 

That  the  nerves  are  destined  to  convey  the 
principles  of  motion  and  sensibility  to  the  brain 
from  all  parts  of  the  system,  there  can  be  no 
doubt  ; but  how  these  effects  are  produced,  no 
one  has  ever  yet  been  able  to  determine.  The 
inquiry  has  been  a constant  source  of  hypothesis 
in  all  ages,  and  has  produced  some  ingenious 
ideas,  and  many  erroneous  positions,  but  with- 
out having  hitherto  afforded  much  satisfactory 
information. 

Some  physiologists  have  considered  a trunk 
of  nerves  as  a solid  chord,  capable  of  being 
divided  into  an  infinite  number  of  filaments, 
by  means  of  which  the  impressions  of  feeling 
are  conveyed  to  the  sensorium  commune. 
Others  have  supposed  it  to  be  a canal,  which 
afterwards  separates  into  more  minute  channels; 
or,  perhaps,  as  being  an  assemblage  of  many 
very  small  and  distinct  tubes,  connected  to 
each  other,  and  thus  forming  a cylindrical 
chord.  They  who  contend  for  their  being 
solid  bodies,  are  of  opinion,  that  feeling  is 
occasioned  by  vibration : so  that,  for  instance 
according  to  this  system,  by  pricking  the 
finger,  a vibration  would  be  occasioned  in  the 
nerve,  distributed  through  its  substance ; and 
the  effects  of  this  vibration,  when  extended  to 
the  sensorium,  would  be  an  excital  of  pain. 
But  the  inelasticity,  the  softness,  the  con- 
nection, and  the  situation  of  the  nerves,  are 
so  many  proofs  that  vibration  has  no  share  in 
the  cause  of  feeling. 

3 C 


386  Of  the  Brain  and  Nerves. 

Others  have  supposed,  that  in  the  brain  and 
spinal  marrow,  a very  subtile  fluid  is  secreted, 
and  from  thence  conveyed  through  tl^e  imper- 
ceptible tubes,  which  they  consider  as  existing 
in  the  nerves.  They  have  farther  supposed, 
that  this  very  subtile  fluid,  to  which  they  have 
given  the  name  of  animal  spirits , is  secreted 
in  the  cortical  substance  of  the  brain  and  spi- 
nal marrow,  from  whence  it  passes  through 
the  medullary  substance.  This,  like  the  other 
system,  is  founded  altogether  on  hypothesis ; 
but  it  seems  to  be  an  hypothesis  derived  from 
much  more  probable  principles,  and  there  are 
many  ingenious  arguments  to  be  brought  in 
its  support. 


EXPLANATION  of  PLATE  XXIX. 

Fig.  1.  Represents  the  Inferior  part  of  the 
Brain; — the  Anterior  part  of  the  whole  Spine, 
including  the  Medulla  Spinalis  ; — with  the 
origin  and  large  portions  of  all  the  Nerves. 

AA,  The  anterior  lobes  of  the  cerebrum. 
BB,  The  lateral  lobes  of  the  cerebrum.  CC, 
The  two  lobes  of  the  cerebellum.  D,  Tuber 
annulare.  E,  The  passage  from  the  third 
ventricle  to  the  infundibulum.  F,  1 he  me- 
dulla oblongata,  which  sends  off  the  medulla 
spinalis  through  the  spine.  G G,  That  part 
of  the  os  occipitis  which  is  placed  above  (H  FI) 
the  transverse  processes  of  the  first  cervical 
vertebra.  I I,  6tc’.  The  seven  cervical  verte- 


OMY  Plate  XXIX 


387 


Of  the  Brain  and  Nerves. 

bras,  with  their  intermediate  cartilages.  K K, 
&c.  The  twelve  dorsal  vertebrae,  with  their 
intermediate  cartilages.  L L,  &tc.  1 he  five 
lumbar  vertebrae,  with  their  intermediate  car- 
tilages. M,  The  os  sacrum.  N,  The  os  coc- 
cyges- 

Nerves. — 1 1,  The  first  pair  of  nerves,  nam- 
ed olfactory , which  go  to  the  nose.  2 2,  The 
second  pair,  named  optic , which  goes  to  form, 
the  tunica  retina  of  the  eye.  3 3,  The  third 
pair,  named  motor  oculi ; it  supplies  most  of 
the  muscles  of  the  eye-ball.  4 4,  The  fourth 
pair,  named  pathetic, — which  is  wholly  spent 
upon  the  musculus  trochlearis  of  the  eye.  5 5, 
The  fifth  pair  divides  into  three  branches. — 
The  first,  named  ophthalmic , goes  to  the  orbit, 
supplies  the  lachrymal  gland,  and  sends 
branches  out  to  the  forehead  and  nose. — - 
The  second,  named  superior  maxillary , sup- 
plies the  teeth  of  the  upper  jaw,  and  some  of 
the  muscles  of  the  lips. — The  third  named  in- 
ferior maxillary , is  spent  upon  the  muscles 
and  teeth  of  the  lower  jaw,  tongue,  and  mus- 
cles of  the  lips.  6 6,  The  sixth  pair,  which, 
after  sending  off  the  beginning  of  the  intercos- 
tal or  great  sympathetic,  is  spent  upon  the  ab- 
ductor oculi.  7 7,  The  seventh  pair,  named 
auditory , divides  into  two  branches. — I he 
largest,  named  portio  mollis,  is  spent  upon  the 
internal  ear.  The  smallest,  portio  dura,  joins 
to  the  fifth  pair  within  the  internal  ear  by  a re- 
flected branch  from  the  second  of  the  fifth ; 
and  within  the  tympanum,  by  a branch  from 
the  third  of  the  fifth  named  chorda  tympani ~ 


388  Of  the  Brain  and  Nerves. 

VicL  fig.  3.  near  B.  8 8,  &c.  The  eighth  pair, 
named  par  vagum , — which  accompanies  the 
intercostal,  and  is  spent  upon  the  tongue,  la- 
rynx, pharynx,  lungs,  and  abdominal  viscera. 
9 9,  The  ninth  pair,  which  are  spent  upon  the 
tongue.  10  10,  &c.  The  intercostal,  or  great 
sympathetic,  which  is  seen  from  the  sixth  pair 
to  the  bottom  of  the  pelvis  on  each  side  of  the 
spine,  and  joining  with  all  the  nerves  of  the 
spine  ; — in  its  progress  supplying  the  heart, 
and,  with  the  par  vagum,  the  contents  of  the 
abdomen  and  pelvis.  11  11,  I he  accessorius, 
which  is  spent  upon  the  sternocleido-mastoi- 
dseus  and  trapezius  muscles.  12  12,  The  first 
cervical  nerves; — 13  13,  The  second  cervical 
nerves  ; — both  spent  upon  the  muscles  that  lie 
on  the  neck,  and  teguments  of  the  neck  and 
head.  14  14,  The  third  cervical  nerves,  which, 
after  sending  olf  (15  15,  &c.)  the  phrenic 
nerves  to  the  diaphragm,  supply  the  muscles 
and  teguments  that  lie  on  the  side  of  the  neck 
and  top  of  the  shoulder.  16  16,  The  brachial 
plexus,  formed  by  the  fourth,  fifth,  sixth,  se- 
venth cervicals,  and  first  dorsal  nerves  ; which 
supply  the  muscles  and  teguments  of  the  su- 
perior extremity.  17  17,  The  twelve  dorsal, 
or  proper  intercostal  nerves,  which  are  spent 
upon  the  intercostal  muscles  and  some  of  the 
large  muscles  which  lie  upon  the  thorax.  18 
18,  The  five  lumbar  pairs  of  nerves,  which 
supply  the  lumbar  and  abdominal  muscles, 
and  some  of  the  teguments  and  muscles  of  the 
inferior  extremity.  19  19,  The  sacro-sciatic, 
or  posterior  crural  nerve,  formed  by  the  two 
inferior  lumbar,  and  three  superior  of  the  os 


Of  the  Brain  and  Nerves.  389 

sacrum.  This  large  nerve  supplies  the  great- 
est part  of  the  muscles  and  teguments  of  the 
inferior  extremity.  20,  The  stomachic  plexus, 
formed  by  the  eighth  pair.  21  21,  Branches 
of  the  solar  or  caeliac  plexus,  formed  by  the 
eighth  pair  and  intercostals,  which  supply  the 
stomach  and  chylopoietic  viscera.  22  22, 
Branches  of  the  superior  and  inferior  mesen- 
teric plexuses,  formed  by  the  eighth  pair  and 
intercostals,  which  supply  the  chylopoietic  vis- 
cera, with  part  of  the  organs  of  urine  and 
generation.  23  23,  Nerves  which  accompany 
the  spermatic  cord.  24  24,  The  hypogastric 
plexus,  which  supplies  the  organs  of  urine 
and  generation  within  the  pelvis. 

Fig.  2,  3,  4,  5.  Shows  different  Views  of  the 
Inferior  part  of  the  Brain,  cut  perpendicu- 
larly through  the  Middle, — with  the  Origin 
and  large  Portions  of  all  the  Nerves  which 
pass  out  through  the  Bones  of  the  Cranium, 
—and  the  three  first  Cervicals. 

A,  The  anterior  lobe.  B,  The  lateral  lobe 
of  the  cerebrum.  C,  One  of  the  lobes  of  the 
cerebellum.  D,  Tuber  annulare.  E,  Corpus 
pyramidale,  in  the  middle  of  the  medulla  ob- 
longata. F,  The  corpus  olivare,  in  the  side 
of  the  medulla  oblongata.  G,  The  medulla  ob- 
longata. H,  The  medulla  spinalis. 

Nerves. — 1 2 3 4 5 6 7 8 and  9,  Pairs  of 
nerves.  10  -10,  Nervus  accessorius,  which 
comes  from — 11,  12,  and  13,  The  three  first 
cervical  nerves. 


390  Of  the  Senses  and  their  Organs. 


PART  VI.  OF  THE  SENSES  AND 
THEIR  ORGANS. 


IN  treating  of  the  senses,  we  mean  to  con- 
fine ourselves  to  the  external  ones  of  touch , 
taste , smelling , hearing , and  vision.  The 
word  sense,  when  applied  to  these  five,  seems 
to  imply  not  only  the  sensation  excited  in  the 
mind  by  certain  impressions  made  on  the  body, 
but  likewise  the  organ  destined  to  receive  and 
transmit  these  impressions  to  the  sensorium. 
Each  of  these  organs  being  of  a peculiar  struc- 
ture, is  susceptible  only  of  particular  impres- 
sions, which  will  be  pointed  out  as  we  pro- 
ceed to  describe  each  of  them  separately. 

Sect.  I.  Of  Touch. 

The  sense  of  touch  maybe  defined  to  be  the 
faculty  of  distinguishing  certain  properties  of 
bodies  by  the  feel.  In  a general  acceptation, 
this  definition  might  perhaps  not  improperly 
be  extended  to  every  part  of  the  body  possess- 
ed of  sensibility,*  but  it  is  commonly  con- 

* In  the  course  of  this  article,  mention  has  often  been  made 
of  the  sensibility  or  insensibility  of  different  parts  of  the  body  : it 
will  therefore,  perhaps,  not  be  amiss  to  observe  in  this  place, 
that  many  parts  which  were  formerly  supposed  to  possess  the 
most  exquisite  sense,  are  now  known  to  have  but  little  or  no 
feeling,  at  least  in  a sound  state  ; for  in  an  inflamed  state,  even 
the  bones,  the  most  insensible  parts  of  any,  become  susceptible 


Of  the  Senses  and  their  Organs.  391 

fined  to  the  nervous  papillae  of  the  cutis,  or 
true  skin,  which,  with  its  appendages,  and 
their  several  uses,  have  been  already  de- 
scribed. 

The  exterior  properties  of  bodies,  such  as 
their  solidity,  moisture,  inequality,  smooth- 
ness, dryness,  or  fluidity,  and  likewise  their 
degree  of  heat,  seem  all  to  be  capable  of  mak- 
ing different  impressions  on  the  papillae,  and 
consequently  of  exciting  different  ideas  in  the 
sensorium  commune.  But  the  organ  of  touch, 
like  all  the  other  senses,  is  not  equally  deli- 
cate in  every  part  of  the  body,  or  in  every 
subject ; being  in  some  much  more  exquisite 
than  it  is  in  others. 

Sect.  II.  Of  the  Taste. 

The  sense  of  taste  is  seated  chiefly  in  the 
tongue  ; the  situation  and  figure  of  which  are 
sufficiently  known. 

On  the  upper  surface  of  this  organ  we  may 
observe  a great  number  of  papillae,  which,  on 
account  of  their  difference  in  size  and  shape, 

of  the  most  painful  sensations.  This  curious  discovery  is  due 
to  the  late  Baron  Haller.  His  experiments  prove,  that  the  bones, 
cartilages,  ligaments,  tendons,  epidermis,  and  membranes  (as 
the  pleura,  pericardium,  dura  and  pia  mater,  periosteum,  &c. 
may  in  a healthy  state  be  considered  as  insensible.  As  sensibility 
depends  on  the  brain  and  nerves,  of  course  different  parts  will 
possess  a greater  or  less  degree  of  feeling,  in  proportion  as  they 
are  supplied  with  a greater  or  smaller  number  of  nerves.  Upon 
this  principle  it  is,  that  the  skin,  muscles,  stomach,  intestines, 
urinary  bladder,  ureters  uterus,  vapina  peni  , tongue,  and  re- 
tina, are  extremely  sensible,  while  the  lungs  and  glands  have 
only  an  obscure  degree  of  feeling. 


392  Of  the  Senses  and  their  Organs. 

are  commonly  divided  into  three  classes.  The 
largest  are  situated  towards  the  basis  of  the 
tongue.  Their  number  commonly  varies  from 
seven  to  nine,  and  they  seem  to  be  mucous 
follicles.  Those  of  the  second  class  are  some- 
what smaller,  and  of  a cylindrical  shape.  They 
are  most  numerous  about  the  middle  of  the 
tongue.  Those  of  the  third  class  are  very 
minute,  and  of  a conical  shape.  They  are 
very  numerous  on  the  apex  and  edges  of  the 
tongue,  and  have  been  supposed  to  be  formed 
by  the  extremities  of  its  nerves. 

We  observe  a line,  the  linea  lingua’  mediana, 
running  along  the  middle  of  the  tongue,  and 
dividing  it  as  it  were  into  two  portions.  To- 
wards the  basis  of  the  tongue,  we  meet  with 
a little  cavity,  named  by  Morgagni  foramen 
ccecum , which  seems  to  be  nothing  more  than 
a common  termination  of  some  of  the  excretory 
ducts  of  mucous  glands  situated  within  the 
substance  of  the  tongue. 

We  have  already  observed,  that  this  organ 
is  every  where  covered  by  the  cuticle,  which, 
by  forming  a reduplication,  called  the  franum , 
at  its  under  part,  serves  to  prevent  the  too 
great  motion  of  the  tongue,  and  to  fix  it  in  its 
situation.  But,  besides  this  attachment,  the 
tongue  is  connected  by  means  of  its  muscles 
and  membranous  ligaments,  to  the  lower  jaw, 
the  os  hyoides,  and  the  styloid  processes. 

The  principal  arteries  of  the  tongue  are  the 
linguales,  which  arise  from  the  external  carotid. 
Its  veins  empty  themselves  into  the  external 
jugulars.  Its  nerves  arise  from  the  fifth,  eighth, 
and  ninth  pair. 


Of  the  Semes  and  their  Organs.  395 

The  variety  of  tastes  seems  to  be  occasioned 
by  the  different  impressions  made  on  the  papil- 
lae by  the  food.  The  different  state  of  the  pa- 
pillae with  respect  to  their  moisture,  their  figure, 
or  their  covering,  seems  to  produce  a consider- 
able difference  in  the  taste,  not  only  in  differ- 
ent people,  but  in  the  same  subject,  in  sickness 
and  in  health.  The  great  use  of  the  taste  seems 
to  be  to  enable  us  to  distinguish  wholesome  and 
salutary  food  from  that  which  is  unhealthy ; and 
we  observe  that  many  quadrupeds,  by  having 
their  papillae*  very  large  and  long,  have  the 
faculty  of  distinguishing  flavours  with  infinite 
accuracy. 

Sect.  III.  Of  Smelling. 

The  sense  of  smelling,  like  the  sense  of  taste-, 
seems  intended  to  direct  us  to  a proper  choice 
of  aliment,  and  is  chiefly  seated  in  the  nose, 
which  is  distinguished  into  its  external  and  in- 
ternal parts.  The  situation  and  figure  of  the 
former  of  these  do  not  seem  to  require  a defini- 
tion. It  is  composed  of  bones  and  cartilages, 
covered  by  muscular  fibres  and  by  the  common 
integuments.  The  bones  make  up  the  upper 
portion,  and  the  cartilages  the  lower  one.  The 
septum  narium,  like  the  nose,  is  likewise  in 
part  bony,  and  in  part  cartilaginous.  These 
bones  and  their  connections  were  described  in 
the  osteology. 

3 D 

* Malpighi’s  description  of  the  papilla;,  which  has  been  copied 
by  many  anatomical  writers,  seems  to  have  been  taken  chiefly 
from  the  tongues  of  sheep. 


394  Of  the  Senses  and  their  Organs . 

The  internal  part  of  the  nose,  besides  the 
ossa  spongiosa,  has  six  cavities  or  sinuses, 
the  maxillary,  the  frontal,  and  the  sphenoid, 
which  were  all  described  with  the  bones  of  the 
head.  They  all  open  into  the  nostrils ; and 
the  nose  likewise  communicates  with  the 
mouth,  larynx,  and  pharynx,  posteriorly  be- 
hind the  velum  palati. 

All  these  several  parts,  which  are  included 
in  the  internal  division  of  the  nose,  viz.  the  in- 
ner surface  of  the  nostrils,  the  lamellae  of  the 
ossa  spongiosa,  and  the  sinuses,  are  lined  by 
a thick  and  very  vascular  membrane,  which, 
though  not  unknown  to  the  ancients,  was  first 
well  described  by  Schneider,*  and  is  therefore 
now  commonly  named  membrana  pituitaria 
Schneideri.  This  membrane  is  truly  the  organ 
of  smelling;  but  its  real  structure  does  not  yet 
seem  to  be  perfectly  understood.  It  appears 
to  be  a continuation  of  the  cuticle,  which  lines 
the  inner  surface  of  the  mouth.  In  some  parts 
of  the  nose  it  is  smooth  and  firm,  and  in  others 
it  is  loose  and  spongy.  It  is  constantly  moist- 
ened by  a mucous  secretion  ; the  finer  parts  of 
which  are  carried  off  by  the  air  we  breathe, 
and  the  remainder,  by  being  retained  in  the 
sinuses,  acquires  considerable  consistence. 
The  manner  in  which  this  mucus  is  secreted 
has  not  yet  been  satisfactorily  ascertained ; but 
it  seems  to  be  by  means  of  mucous  follicles. 

Its  arteries  are  branches  of  the  internal  max- 
illary and  internal  carotid.  Its  veins  empty 
themselves  into  the  internal  jugulars.  The 
first  pair  of  nerves,  the  olfactory,  are  spread 


* De  Catarrho,  lib.  iii. 


Of  the  Senses  and  their  Organs.  395 

over  every  part  of  it,  and  it  likewise  receives 
branches  from  the  fifth  pair. 

After  what  has  been  said  of  the  pituitary 
membrane,  it  will  not  be  difficult  to  conceive 
how  the  air  we  draw  in  at  the  nostrils,  being 
impregnated  with  the  effluvia  of  bodies,  ex- 
cites in  us  that  kind  of  sensation  we  call  smell- 
ing. As  these  effluvia,  from  their  being  ex- 
ceedingly light  and  volatile,  cannot  be  capable 
in  a small  quantity  of  making  any  great  im- 
pression on  the  extremities  of  the  olfactory 
nerves,  it  was  necessary  to  give  considerable 
extent  to  the  pituitary  membrane,  that  by  this 
means  a greater  number  of  odoriferous  parti- 
cles might  be  admitted  at  the  same  time.  When 
we  wish  to  take  in  much  of  the  effluvia  of  any 
thing,  we  naturally  close  the  mouth,  that  all 
the  air  we  inspire  may  pass  through  the  nos- 
trils ; and  at  the  same  time,  by  means  of  the 
muscles  of  the  nose,  the  nostrils  are  dilated, 
and  a greater  quantity  of  air  is  drawn  into 
them. 

In  many  quadrupeds,  the  sense  of  smelling 
is  much  more  extensive  and  delicate  than  it  is 
in  the  human  subject ; and  in  the  human  sub- 
ject it  seems  to  be  more  perfect  the  less  it  is 
vitiated  by  a variety  of  smells.  It  is  not  al- 
ways in  the  same  state  of  perfection,  being  na- 
turally affected  by  every  change  of  the  pitui- 
tary membrane,  and  of  the  lymph  with  which 
that  membrane  is  moistened. 


3 96  Of  the  Senses  and  their  Organs. 


Sect.  IV.  Of  Hearing. 

Before  we  undertake  to  explain  the  man- 
ner in  which  we  are  enabled  to  receive  the  im- 
pressions of  sound,  it  will  be  necessary  to  de- 
scribe the  ear,  which  is  the  organ  of  hearing. 
It  is  commonly  distinguished  into  external  and 
internal.  The  former  of  these  divisions  in- 
cludes all  that  we  are  able  to  discover  without 
dissection,  and  the  meatus  auditorius,  as  far 
as  the  tympanum and  the  latter,  all  the  other 
parts  of  the  ear. 

The  external  ear  is  a cartilaginous  funnel, 
covered  by  the  common  integuments,  and  at- 
tached, by  means  of  its  ligaments  and  muscles* 
to  the  temporal  bone.  Although  capable  only 
of  a very  obscure  motion,  it  is  found  to  have 
several  muscles.  Different  parts  of  it  are  dis- 
tinguished by  several  names  ; all  its  cartila- 
ginous part  is  called  ala  or  wing , to  distin- 
guish it  from  the  soft  and  pendent  part  below, 
called  the  lobe . Its  outer  circle  or  border  is 
called  helix , and  the  semicircle  within  this, 
antihelix.  The  moveable  cartilage  placed  im- 
mediately before  the  meatus  auditorius,  which 
it  may  be  made  to  close  exactly,  is  named 
tragus ; and  an  eminence  opposite  to  this  at 
the  extremity  of  the  antihelix,  is  called  anti- 
tragus. The  concha  is  a considerable  cavity 
formed  by  the  extremities  of  the  helix  and  an- 
tihelix. The  meatus  auditorius,  which  at  its 
opening  is  cartilaginous,  is  lined  with  a very 
thin  membrane,  which  is  a continuation  of  the 
fcuticle  from  the  surface  of  the  ear. 


Of  the  Senses  and  their  Organs.  397 

In  this  canal  we  find  a yellow  wax,  which 
is  secreted  by  a number  of  minute  glands  or 
follicles,  each  of  which  has  an  excretory  duct. 
This  secretion,  which  is  at  first  of  an  oily  con- 
sistence, defends  the  membrane  of  the  tym- 
panum from  the  injuries  of  the  air  ; and  by  its 
bitterness,  prevents  minute  insects  from  enter- 
ing into  the  ear.  But  when  from  neglect  or 
disease  it  accumulates  in  too  great  a quantity, 
it  sometimes  occasions  deafness.  The  inner 
extremity  of  the  meatus  is  closed  by  a very 
thin  transparent  membrane,  the  membrana 
tympani,  which  is  set  in  a bony  circle  like  the 
head  of  a drum.  In  the  last  century  Rivinus, 
professor  at  Liepsic,  fancied  he  had  discovered 
a hole  in  this  membrane,  surrounded  by  a 
sphincter,  and  affording  a passage  to  the  air, 
between  the  external  and  internal  ear.  Cow- 
per,  Heister,  and  some  other  anatomists,  have 
admitted  this  supposed  foramen,  which  cer- 
tainly does  not  exist.  Whenever  there  is  any 
opening  in  the  membrana  tympani,  it  may  be 
considered  as  accidental.  Under  the  mem- 
brana tympani  runs  a branch  of  the  fifth  pair 
of  nerves,  called  chorda  tympani ; and  beyond 
this  membrane  is  the  cavity  of  the  tympanum, 
which  is  about  seven  or  eight  lines  wide,  and 
half  so  many  in  depth  ; it  is  semispherical,  and 
every  where  lined  by  a very  fine  membrane. 
There  are  four  openings  to  be  observed  in  this 
cavity.  It  communicates  with  the  mouth  by 
means  of  the  Eustachian  tube.  This  canal, 
- which  is  in  part  bony  and  in  part  cartilaginous, 
begins  by  a very  narrow  opening  at  the  anteri- 
or and  almost  superior  part  of  the  tympanum. 


398  Of  the  'Senses  and  their  Organs. 

increasing  in  size  as  it  advances  towards  the 
palate  of  the  mouth,  where  it  terminates  by 
an  oval  opening.  This  tube  is  every  where 
lined  by  the  same  membrane  that  covers  the 
inside  of  the  mouth.  The  real  use  of  this  ca- 
nal does  not  seem  to  have  been  hitherto  satis- 
factorily ascertained ; but  sound  would  seem 
to  be  conveyed  through  it  to  the  membrana 
tympani,,  deaf  persons  being  often  observed 
to  listen  attentively  with  their  mouths  open. 
Opposite  to  this  is  a minute  passage,  which 
leads  to  the  sinuosities  of  the  mastoid  process  ; 
and  the  two  other  openings,  which  are  in  the 
internal  process  of  the  os  petrosum,  are  the 
fenestra  ovalis,  and  fenestra  rotunda,  both  of 
which  are  covered  by  a very  fine  membrane. 

There  are  three  distinct  bones  in  the  cavity 
of  the  tympanum ; and  these  are  the  malleus, 
incus,  and  stapes.  Besides  these  there  is  a 
fourth,  which  is  the  os  orhiculare , considered 
by  some  anatomists  as  a process  of  the  stapes, 
which  is  necessarily  broken  off  by  the  violence 
we  are  obliged  to  use  in  getting  at  these 
bones ; but  when  accurately  considered,  it 
seems  to  be  a distinct  bone. 

The  malleus  is  supposed  to  resemble  a ham- 
mer, being  larger  at  one  extremity,  which  is 
its  head,  than  it  is  at  the  other,  which  is  its 
handle.  The  latter  is  attached  to  the  mem- 
brana tympani,  and  the  head  of  the  bone  is 
articulated  with  the  incus. 

The  incus , as  it  is  called  from  its  shape, 
though  it  seems  to  have  less  resemblance  to 
an  anvil  than  to  one  of  the  dentes  molares  with 
its  roots  widely  separated  from  each  other,  is 


Of  the  Senses  and  their  Organs.  399 

distinguished  into  its  body  and  its  legs.  One 
of  its  legs  is  placed  at  the  entry  of  the  canal 
which  leads  to  the  mastoid  process  ; and  the 
other,  which  is  somewhat  longer,  is  articulat- 
ed with  the  stapes,  or  rather  with  the  os  orbi- 
culare,  which  is  placed  between  them. 

The  third  bone  is  very  properly  named 
stapes , being  perfectly  shaped  like  a stirrup. 
Its  basis  is  fixed  into  the  fenestra  ovalis,  and 
its  upper  part  is  articulated  with  the  os  orbicu- 
lare.  What  is  called  the  fenestra  rotunda, 
though  perhaps  improperly,  as  it  is  more  oval 
than  round,  is  observed  a little  above  the 
other,  in  an  eminence  formed  by  the  os  petro- 
sum,  and  is  closed  by  a continuation  of  the 
membrane  that  lines  the  inner  surface  of  the 
tympanum.  The  stapes  and  malleus  are  each 
of  them  furnished  with  a little  muscle,  the  sta- 
pedeus  and  tensor  tympani.  The  first  of  these, 
which  is  the  smallest  in  the  body,  arises  from 
a little  cavern  in  the  posterior  and  upper  part 
of  the  cavity  of  the  tympanum  ; and  its  tendon, 
after  passing  through  a hole  in  the  same  ca- 
vern, is  inserted  at  the  back  part  of  the  head 
of  the  stapes.  This  muscle,  by  drawing  the 
stapes  obliquely  upwards,  assists  in  stretch- 
ing the  membrana  tympani. 

The  tensor  tympani,*  or  interims  mallei,  as 
it  is  called  by  some  writers,  arises  from  the 
cartilaginous  extremity  of  the  Eustachian  tube, 
and  is  inserted  into  the  back  part  of  the  handle 

* Some  anatomists  describe  three  muscles  of  the  malleus ; but 
only  this  one  seems  to  deserve  the  name  of  muscle ; what  are 
called  the  externus  and  obliquas  mallei,  seeming  to  be  ligaments 
rather  titan  muscles. 


400  Of  the  Senses  and  their  Organs . 

of  the  malleus*  which  it  serves  to  pull  inwards, 
and  of  course  helps  to  stretch  the  membrana 
tympani. 

The  labyrinth  is  the  only  part  of  the  ear 
which  remains  to  be  described.  It  is  situated 
in  the  os  petrosum,  and  is  separated  from  the 
tympanum  by  a partition  which  is  every  where 
bony,  except  at  the  two  fenestrae.  It  is  com- 
posed of  three  parts  ; and  these  are  the  vesti- 
bulum,  the  semicircular  canals,  and  the  coch- 
lea. 

The  vestibulum  is  an  irregular  cavity,  much 
smaller  than  the  tympanum,  situated  nearly  in 
the  centre  of  the  os  petrosum,  between  the 
tympanum,  the  cochlea,  and  the  semicircular 
canals.  It  is  open  on  the  side  of  the  tympa- 
num by  means  of  the  fenestra  ovalis,  and  com- 
municates with  the  upper  portion  of  the  coch- 
lea by  an  oblong  foramen,  which  is  under  the 
fenestra  ovalis,  from  which  it  is  separated  only 
by  a very  thin  partition. 

Each  of  the  three  semicircular  canals  forms 
about  half  a circle  of  nearly  a line  in  diameter, 
and  running  each  in  a different  direction,  they 
are  distinguished  into  vertical , oblique , and  ho- 
rizontal. These  three  canals  open  by  both 
their  extremities  into  the  vestibulum  ; but  the 
vertical  and  the  oblique  being  united  together 
at  one  of  their  extremities,  there  are  only  five 
orifices  to  be  seen  in  the  vestibulum. 

The  cochlea  is  a canal  which  takes  a spiral 
course,  not  unlike  the  shell  of  a snail.  From 
its  basis  to  its  apex  it  makes  two  turns  and  a 
half ; and  is  divided  into  two  canals  by  a very 
thin  lamina  or  septum,  which  is  in  part  bony 


Of  the  Senses  and  their  Organs.  401 

and  in  part  membranous,  in  such  a manner 
that  these  two  canals  only  communicate  with 
each  other  at  the  point.  One  of  them  opens 
into  the  vestibulum,  and  the  other  is  covered 
by  the  membrane  that  closes  the  fenestra  ro- 
tunda. The  bony  lamella  which  separates  the 
two  canals  is  exceedingly  thin,  and  fills  about 
two-thirds  of  the  diameter  of  the  canal.  The 
rest  of  the  septum  is  composed  of  a most  deli- 
cate membrane,  which  lines  the  whole  inner 
surface  of  the  cochlea,  and  seems  to  form  this 
division  in  the  same  manner  as  the  two  mem- 
branous bags  of  the  pleura,  by  being  applied 
to  each  other,  form  the  mediastinum. 

Every  part  of  the  labyrinth  is  furnished  with 
a very  delicate  periosteum,  and  filled  with  a 
watery  fluid,  secreted  as  in  other  cavities.  This 
fluid  transmits  to  the  nerves  the  vibrations  it 
receives  from  the  membrane  closing  the  fenes- 
tra rotunda,  and  from  the  basis  of  the  stapes, 
where  it  rests  on  the  fenestrum  ovale.  When 
this  fluid  is  collected  in  too  great  a quantity, 
or  is  compressed  by  the  stapes,  it  is  supposed 
to  escape  through  two  minute  canals  or  aque- 
ducts, lately  described  by  Dr.  Cotunni,*  an  in- 
genious physician  at  Naples.  One  of  these 
aqueducts  opens  into  the  bottom  of  the  ves- 
tibulum, and  the  other  into  the  cochlea,  near 
the  fenestra  rotunda.  They  both  pass  through 
the  os  petrosum,  and  communicate  with  the  ca- 
vity of  the  cranium  where  the  fluid  that  passes 
through  them  is  absorbed ; and  they  are  lined 

3 E 


r*  De  aqu®ductibus  Auris  Human®  Intern®,  8vo,  1760. 


402  Of  the  Senses  and  their  Organs , 

by  a membrane  which  is  supposed  to  be  a pro- 
duction of  the  dura  mater. 

The  arteries  of  the  external  ear  come  from 
the  temporal  and  other  branches  of  the  exter- 
nal carotid,  and  its  veins  pass  into  the  jugular. 
The  internal  ear  receives  branches  of  arteries 
from  the  basilary  and  carotids,  and  its  veins 
empty  themselves  into  the  sinuses  of  the  dura 
mater,  and  into  the  internal  jugular. 

The  portio  mollis  of  the  seventh  pair  is  dis- 
tributed through  the  cochlea,  the  vestibulumr 
and  the  semi-circular  canals  ; and  the  portio 
dura  sends  off  a branch  to  the  tympanum,  and 
other  branches  to  the  external  ear  and  parts 
near  it. 

The  sense  of  hearing , in  producing  which 
all  the  parts  we  have  described  assist,  is  occa- 
sioned by  a certain  modulation  of  the  air  col- 
lected by  the  funnel-like  shape  of  the  external 
ear,  and  conveyed  through  the  meatus  audito- 
rius  to  the  membrana  tympanh  That  sound 
is  propagated  by  means  of  the  air,  is  very  ea- 
sily proved  by  ringing  a bell  under  the  receiv- 
er of  an  air-pump the  sound  it  affords  being 
found  to  diminish  gradually  as  the  air  becomes 
exhausted,  till  at  length  it  ceases  to  be  heard 
at  all.  Sound  moves  through  the  air  with  in- 
finite velocity ; but  the  degree  of  its  motion 
seems  to  depend  on  the  state  of  the  air,  as  it 
constantly  moves  faster  in  a dense  and  dry, 
than  it  does  in  a moist  and  rarefied  air. 

That  the  air  vibrating  on  the  membrana 
tympani  communicates  its  vibration  to  the  dif- 
ferent parts  of  the  labyrinth,  and  by  means  of 


Of  the  Senses  and  their  Organs.  403 


the  fluid  contained  in  this  cavity  affects  the  au- 
ditory nerve  so  as  to  produce  sound,  seems  to 
be  very  probable  ; but  the  situation,  the  mi- 
nuteness, and  the  variety  of  the  parts  which 
compose  the  ear,  do  not  permit  much  to  be  ad- 
vanced with  certainty  concerning  their  mode  of 
action. 

Some  of  these  parts  seem  to  constitute  the 
immediate  organ  of  hearing,  and  these  are  all 
the  parts  of  the  vestibulum.:  but  there  are  others 
which  seem  intended  for  the  perfection  of  this 
sense,  without  being  absolutely  essential  to  it. 
It  has  happened,  for  instance,  that  the  mem- 
brana  tympani,  and  the  little  bones  of  the  ear, 
have  been  destroyed  by  disease,  without  de- 
priving the  patient  of  the  sense  of  hearing.* 

Sound  is  more  or  less  loud  in  proportion  to 
the  strength  of  the  vibration and  the  variety 
of  sounds  seems  to  depend  on  the  difference 
of  this  vibration  ; for  the  more  quick  and  fre- 
quent it  is,  the  more  acute  will  be  the  sound, 
and  vice  versa. 

Before  we  conclude  this  article,  it  will  be 
right  to  explain  certain  phenomena,  which  will 
be  found  to  have  a relation  to  the  organ  of 
hearing. 

Every  body  has,  in  consequence  of  particu- 
lar sounds,  occasionally  felt  that  disagreeable 
sensation  which  is  usually  called  setting  the 
teeth  on  edge : and  the  cause  of  this  sensation 

* This  observation  has  led  to  a supposition,  that  a perforation 
of  this  membrane  may  in  some  cases  of  deafness  be  useful  ; and 
Mr.  Cheselden  relates,  that,  some  years  ago,  a malefactor  was 
pardoned  on  condition  that  he  should  submit  to  this  operation  ; 
but  the  public  clamour  raised  against  it  was  so  great,  that  it  was 
•thought  right  not  to  perform  it. 


404  Of  the  Senses  and  their  Organs. 

may  be  traced  to  the  communication  which  the 
portio  dura  of  the  auditory  nerve  has  with  the 
branches  of  the  fifth  pair  that  are  distributed 
to  the  teeth,  being  probably  occasioned  by  the 
violent  tremor  produced  in  the  membrana  tym- 
pani  by  these  very  acute  sounds.  Upon  the 
same  principle  we  may  explain  the  strong  idea 
of  sound  which  a person  has  who  holds  a vi- 
brating string  between  his  teeth. 

The  humming  which  is  sometimes  perceiv- 
ed in  the  ear,  without  any  exterior  cause,  may- 
be occasioned  either  by  an  increased  action  of 
the  arteries  in  the  ears,  or  by  convulsive  con- 
tractions of  the  muscles  of  the  malleus  and 
stapes,  affecting  the  auditory  nerve  in  such  a 
manner  as  to  produce  the  idea  of  sound.  An 
ingenious  philosophical  writer*  has  lately  dis- 
covered that  there  are  sounds  liable  to  be  ex- 
cited in  the  ear  by  irritation,  and  without  any 
assistance  from  the  vibrations  of  the  air. 


Sect.  V.  Of  Vision. 

The  eyes,  which  constitute  the  organ  of  vi- 
sion, are  situated  in  two  bony  cavities  named 
orbits , where  they  are  surrounded  by  several 
parts,  which  are  either  intended  to  protect 
them  from  external  injury,  or  to  assist  in  their 
motion. 

The  globe  of  the  eye  is  immediately  covered 
by  two  eye-lids  or  palpebrae,  which  are  com- 

* Elliot’s  Philosophkal  Observations  on  the  Senses  of  Vision 
and  Hearing,  8vo. 


Of  the  Senses  and  their  Organs.  405 

posed  of  muscular  fibres  covered  by  the  com- 
mon integuments,  and  lined  by  a very  fine  and 
smooth  membrane,  which  is  from  thence  ex- 
tended over  part  of  the  globe  of  the  eye,  and 
is  called  tunica  conjunctiva.  Each  eye-lid  is 
cartilaginous  at  its  edge  ; and  this  border  which 
is  called  tarsus , is  furnished  with  a row  of  hairs 
named  cilia  or  eye-lashes. 

The  cilia  serve  to  protect  the  eye  from  in- 
sects and  minute  bodies  floating  in  the  air,  and 
likewise  to  moderate  the  action  of  the  rays  of 
light  in  their  passage  to  the  retina.  At  the 
roots  of  these  hairs  there  are  sebaceous  folli- 
cles, first  noticed  by  Meibomius,  which  dis- 
charge a glutinous  liniment.  Sometimes  the 
fluid  they  secrete  has  too  much  viscidity,  and 
the  eye-lids  become  glued  to  each  other. 

The  upper  border  of  the  orbit  is  covered  by 
the  eye-brows  or  supercilia,  which  by  means 
of  their  two  muscles  are  capable  of  being 
brought  towards  each  other,  or  of  being  carried 
upwards.  They  have  been  considered  as  serv- 
ing to  protect  the  eyes,  but  they  are  probably 
intended  more  for  ornament  than  utility.* 

The  orbits  in  which  the  eyes  are  placed,  are 
furnished  with  a good  deal  of  fat,  which  af- 
fords a soft  bed  on  which  the  eye  performs  its 
several  motions.  The  inner  angle  of  each  or- 
bit, or  that  part  of  it  which  is  near  the  nose,  is 
called  cantlius  major , or  the  great  angle ; and 
the  outer  angle,  which  is  on  the  opposite  side 
of  the  eye,  is  the  canthus  minor , or  little  angle. 

* It  is  observable,  that  the  eye-brows  are  peculiar  to  the  hu- 
man species. 


406  Of  the  Senses  and  their  Organs. 

The  little  reddish  body  which  we  observe 
in  the  great  angle  of  the  eye-lids,  and  which  is 
called  caruncula  lachrymalis , is  supposed  to  be 
ol  a glandular  structure,  and,  like  the  follicles 
of  the  eye-lids,  to  secrete  an  oily  humour.  But 
its  structure  and  use  do  not  seem  to  have  been 
hitherto  accurately  determined.  The  surface 
of  the  eye  is  constantly  moistened  by  a very 
fine  limpid  fluid  called  the  tears,  which  is  chief- 
ly, and  perhaps  wholly,  derived  from  a large 
gland  of  the  conglomerate  kind,  situated  in  a 
small  depression  of  the  os  frontis  near  the  out- 
er angle  of  the  eye.  Its  excretory  ducts  pierce 
the  tunica  conjunctiva  just  above  the  cartila- 
ginous borders  of  the  upper  eye-lids.  When 
the  tears  were  supposed  to  be  secreted  by  the 
caruncule,  this  gland  was  called  glandula  inno- 
minata ; but  now  that  its  structure  and  uses 
are  ascertained,  it  very  properly  has  the  name 
of  glandula  lachrymalis.  The  tears  poured 
out  by  the  ducts  of  this  gland  are,  in  a natur- 
al and  healthy  state,  incessantly  spread  over  the 
surface  of  the  eye,  to  keep  it  clear  and  trans- 
parent, by  means  of  the  eye-lids,  and  as  con- 
stantly pass  out  at  the  opposite  corner  of  the 
eye  or  inner  angle,  through  two  minute  orifi- 
ees,  the  puncta  lachrymalia  being  determined 
into  these  little  openings  by  a reduplication  of 
the  tunica  conjunctiva,  shaped  like  a crescent 
the  two  points  of  which  answer  to  the  puncta. 

* It  sometimes  happens,  that  this  very  pellucid  fluid,  which 
moistens  the  eye,  being  poured  out  through  the  excretory  ducts 
of  the  lachrymal  gland  faster  than  it  can  be  carried  off  through 
the  puncta,  trickles  down  the  cheek,  and  is  then  strictly  and  pro- 
perly called  tears. 


Of  the  Senses  and  their  Organs.  407 

This  reduplication  is  named  membrana , or  val- 
vula  semilunaris.  Each  of  these  puncta  is  the 
beginning  of  a small  excretory  tube,  through 
which  the  tears  pass  into  a little  pouch  or  re- 
servoir,  the  sacculus  lachrymalis,  which  lies 
in  an  excavation  formed  partly  by  the  nasal 
process  of  the  os  maxillare  superius,  and  part- 
ly by  the  os  unguis.  The  lower  part  of  this 
sac  forms  a duct  called  the  ductus  ad  nares, 
which  is  continued  through  a bony  channel, 
and  opens  into  the  nose,  through  which  the 
tears  are  occasionally  discharged.* 

The  motions  of  the  eye  are  performed  by 
six  muscles  ; four  of  which  are  straight  and 
two  oblique.  The  straight  muscles  are  dis- 
tinguished by  the  names  of  elevator , depres- 
sor, adductor , and  abductor,  from  their  se- 
veral uses  in  elevating  and  depressing  the  eye, 
drawing  it  towards  the  nose,  or  carrying  it 
from  the  nose  towards  the  temple.  All  these 
four  muscles  arise  from  the  bottom  of  the  or- 
bit, and  are  inserted  by  flat  tendons  into  the 
globe  of  the  eye.  The  oblique  muscles  are 
intended  for  the  more  compound  motions  of  the 
eye.  The  first  of  these  muscles,  the  obli- 
quus  superior,  does  not,  like  the  other  four  mus- 
cles we  have  described,  arise  from  the  bottom 
of  the  orbit,  but  from  the  edge  of  the  fora- 
men that  transmits  the  optic  nerve,  which  se- 
parates the  origin  of  this  muscle  from  that  of 

* When  the  ductus  ad  nares  becomes  obstructed  in  conse- 
quence of  disease,  the  tears  are  no  longer  able  to  pass  into  the  nos* 
trilji ; the  sacculus  lachrymalis  becomes  distended  ; and  inflam- 
mation, and  sometimes  ulceration  taking  place,  constitute  the 
disease  called  fistula  lachrymalis. 


408  Of  the  Senses  and  their  Organs . 

the  others.  From  this  beginning  it  passes  ill 
a straight  line  towards  a very  small  cartilagin- 
ous ring,  the  situation  of  which  is  marked  in 
the  skeleton  by  a little  hollow  in  the  internal 
orbitar  process  of  the  os  frontis.  The  tendon 
of  the  muscle  after  passing  through  this  ring, 
is  inserted  into  the  upper  part  of  the  globe  of 
the  eye,  which  it  serves  to  draw  forwards,  at 
the  same  time  turning  the  pupil  downwards. 

The  obliquus  inferior  arises  from  the  edge 
of  the  orbit,  under  the  opening  of  the  ductus 
lachrymalis  ; and  is  inserted  somewhat  poste- 
riorly into  the  outer  side  of  the  globe,  serving 
to  draw  the  eye  forwards  and  turn  the  pupil 
upwards.  When  either  of  these  two  muscles 
acts  separately,  the  eye  is  moved  on  its  axis ; 
but  when  they  act  together,  it  is  compressed 
both  above  and  below.  The  eye  itself,  which 
is  now  to  be  described,  with  its  tunics,  hu- 
mours, and  component  parts,  is  nearly  of  a 
spherical  figure.  Of  its  tunics,  the  conjuncti- 
va has  been  already  described  as  a partial  co- 
vering, reflected  from  the  inner  surface  of  the 
eye-lids  over  the  anterior  portion  of  the  eye. 
What  has  been  named  albuginea  cannot  pro- 
perly be  considered  as  a coat  of  the  eye,  being 
in  fact  nothing  more  than  the  tendons  of  the 
straight  muscles  spread  over  some  parts  of  the 
sclerotica. 

The  immediate  tunics  of  the  eye,  which  are 
to  be  demonstrated  when  its  partial  coverings, 
and  all  the  other  parts  with  which  it  is  sur- 
rounded, are  removed,  are  the  sclerotica,  cor- 
nea, choroides,  and  retina. 


Of  the  Senses  and  their  Organs.  409 

The  sclerotica , which  is  the  exterior  coat, 
is  every  where  white  and  opaque,  and  is  join- 
ed at  its  anterior  edge  to  another,  which  has 
more  convexity  than  any  other  part  of  the 
globe,  and  being  exceedingly  transparent  is 
called  cornea .*  These  two  parts  are  perfectly 
different  in  their  structure ; so  that  some  ana- 
tomists suppose  them  to  be  as  distinct  from 
each  other  as  the  glass  of  a watch  is  from  the 
case  into  which  it  is  fixed.  The  sclerotica  is 
of  a compact  fibrous  structure  'r  the  cornea,  on 
the  other  hand,  is  composed  of  a great  num- 
ber of  laminae  united  by  cellular  membrane. 
By  macerating  them  in  boiling  water,  they  do 
not  separate  from  each  other,  as  some  writers 
have  asserted ; but  the  cornea  soon  softens, 
and  becomes  of  a glutinous  consistence. 

The  ancients  supposed  the  sclerotica  to  be  a 
continuation  of  the  dura  mater.  Morgagni,  and 
some  other  modern  writers,  are  of  the  same 
opinion  ; but  this  point  is  disputed  by  Winslow, 
Haller,  Zin,  and  others.  The  truth  seems  to 
be,  that  the  sclerotica,  though  not  a production 
of  the  dura  mater,  adheres  intimately  to  that 
membrane. 

The  choroides  is  so  called  because  it  is  fur- 
nished with  a great  number  of  vessels.  It  has 
likewise  been  named  uvea,  on  account  of  its  re- 
semblance to  a grape.  Many  modern  anatomi- 
cal writers  have  considered  it  as  a production 
of  the  pia  mater.  This  was  likewise  the  opinion 

3 F 

* Some  writers,  who  have  given  the  name  of  cornea  to  all  this 
outer  coat,  have  named  what  is  here  and  most  commonly  called 
sclerotica,  cornea  opaca  ; and  its  anterior  and  transparent  portion, 
cornea  luctda. 


410  Of  the  Senses  and  their  Organs. 

of  the  ancients  ; but  the  strength  and  thickness 
of  the  choroides,  when  compared  with  the  deli- 
cate structure  of  the  pia  mater,  are  sufficient 
proofs  of  their  being  two  distinct  membranes. 

The  choroides  has  of  late  generally  been  de- 
scribed as  consisting  of  two  laminae  ; the  inner- 
most of  which  has  been  named  after  Ruysch, 
who  first  described  it.  It  is  certain,  however, 
that  Ruysch’s  distinction  is  ill  founded,  at  least 
with  respect  to  the  human  eye,  in  which  we  are 
unable  to  demonstrate  any  such  structure,  al- 
though the  tunica  choroides  of  sheep  and  some 
other  quadrupeds  may  easily  be  separated  into 
two  layers. 

The  choroides  adheres  intimately  to  the  scle- 
rotica round  the  edge  of  the  cornea  ; and  at  the 
place  of  this  union,  we  may  observe  a little 
whitish  areola,  named  ligamentum  ciliare , 
though  it  is  not  of  a ligamentous  nature. 

They  who  suppose  the  choroides  to  be  com- 
posed of  two  laminae,  describe  the  external  one 
as  terminating  in  the  ligamentum  ciliare,  and 
the  internal  one  as  extending  farther  to  form  the 
iris,  which  is  the  circle  we  are  able  to  distin- 
guish through  the  cornea  ; but  this  part  is  of  a 
very  different  structure  from  the  choroides ; 
so  that  some  late  writers  have  perhaps  not  im- 
properly considered  the  iris  as  a distinct  mem- 
brane. It  derives  its  name  from  the  variety  of 
its  colours,  and  is  perforated  in  the  middle. — 
This  perforation,  which  is  called  the  pupil  or 
sight  of  the  eye,  is  closed  in  the  foetus  by  a very 
thin  vascular  membrane.  This  membrana  pu- 
pillaris  commonly  disappears  about  the  seventh 
month. 


Of  the  Senses  and  their  Organs.  411 

On  the  under  side  of  the  iris  we  observe  ma- 
ny minute  fibres,  called  ciliary  processes , which 
pass  in  radii  or  parallel  lines  from  the  circum- 
ference to  the  centre.  The  contraction  and 
dilatation  of  the  pupil  are  supposed  to  depend 
on  the  action  of  these  processes.  Some  have 
considered  them  as  muscular,  but  they  are 
not  of  an  irritable  nature:  others  have  sup- 
posed them  to  be  filaments  of  nerves ; but 
their  real  structure  has  never  yet  been  clearly 
ascertained. 

Besides  these  ciliary  processes,  anatomists 
usually  speak  of  the  circular  fibres  of  the  iris, 
but  no  such  seem  to  exist. 

The  posterior  surface  of  the  iris,  the  ciliary 
processes,  and  part  of  the  tunica  choroides, 
are  covered  by  a black  mucus  for  the  purposes 
of  accurate  and  distinct  vision ; but  the  man- 
ner in  which  it  is  secreted  has  not  been  deter- 
mined. 

Immediately  under  the  tunica  choroides  we 
find  the  third  and  inner  coat,  called  the  retina , 
which  seems  to  be  merely  an  expansion  of  the 
pulpy  substance  of  the  optic  nerve,  extending 
to  the  border  of  the  crystalline  humour. 

The  greatest  part  of  the  globe  of  the  eye, 
within  these  several  tunics,  is  filled  by  a very 
transparent  and  gelatinous  humour  of  conside- 
rable consistence,  which,  from  its  supposed 
resemblance  to  fused  glass,  is  called  the  vitre- 
ous humour.  It  is  invested  by  a very  fine  and 
delicate  membrane,  called  tunica  vitrea , and 
sometimes  arachnoicles. — It  is  supposed  to  be 
composed  of  two  laminae  ; one  of  which  dips 
into  its  substance,  and  by  dividing  the  hu- 


412  Of  the  Senses  and  their  Organs , 


mour  into  cells  adds  to  its  firmness.  The 
fore-part  of  the  vitreous  humour  is  a little 
hollowed,  to  receive  a very  white  and  trans- 
parent substance  of  a firm  texture,  and  of  a 
lenticular  and  somewhat  convex  shape,  named 
the  crystalline  humour.  It  is  included  in  a 
capsula,  which  seems  to  be  formed  by  a sepa- 
ration of  the  two  laminae  of  the  tunica  vitrea. 

The  fore-part  of  the  eye  is  filled  by  a very 
thin  and  transparent  fluid,  named  the  aqueous 
humour , which  occupies  all  the  space  between 
the  crystalline  and  the  prominent  cornea — 
The  part  of  the  choroides  which  is  called  the 
iris,  and  which  comes  forward  to  form  the 
pupil,  appears  to  be  suspended  as  it  were  in 
this  humour,  and  has  occasioned  this  portion 
of  the  eye  to  be  distinguished  into  two  parts. 
One  of  these,  which  is  the  little  space  between 
the  anterior  surface  of  the  crystalline  and  the 
iris,  is  called  the  posterior  chamber;  and  the 
other,  which  is  the  space  between  the  iris  and 
the  cornea,  is  called  the  anterior  chamber  of 
the  eye.*  Both  these  spaces  are  completely 
filled  with  the  aqueous  humour.f 

* We  are  aware  that  some  anatomists,  particularly  Lieutaud, 
are  of  opinion,  that  the  iris  is  every  where  in  close  contact  with 
the  crystalline,  and  that  it  is  of  course  right  to  speak  only  of  one 
chamber  of  the  eye  ; but  as  this  does  not  appear  to  be  the  case, 
the  situation  cf  the  iris  and  the  two  chambers  of  the  eye  are  here 
described  in  the  usual  way. 

f When  the  crystalline  becomes  opaque,  so  as  to  prevent  the 
passage  of  the  rays  of  light  to  the  retina,  it  constitutes  what  is 
called  a cataract ; and  the  operation  of  couching  consists  in  re- 
moving the  diseased  crystalline  from  its  bed  in  the  vitreous  hu- 
mour. In  this  operation  the  cornea  is  perforated,  and  the  aque- 
ous humour  escapes  out  of  the  eye,  but  it  is  constantly  renewed 
again  in  a very  short  time.  The  manner,  however,  in  which  it 
is  secreted,  has  not  yet  been  determined. 


Of  the  Senses  and  their  Organs.  415 

The  eye  receives  its  arteries  from  the  in- 
ternal carotid  through  the  foramina  optica ; 
and  its  veins  pass  through  the  foramina  lacera, 
and  empty  themselves  into  the  lateral  sinuses. 
Some  of  the  ramifications  of  these  vessels  ap- 
pear on  the  inner  surface  of  the  iris,  where 
they  are  seen  to  make  very  minute  convolu- 
tions, which  are  sufficiently  remarkable  to  be 
distinguished  by  the  name  of  circulus  arteriosus , 
though  perhaps  improperly,  as  they  are  chief- 
ly branches  of  veins. 

The  optic  nerve  passes  in  at  the  posterior 
part  of  the  eye,  in  a considerable  trunk,  to  be 
expanded  for  the  purposes  of  vision,  of  which 
it  is  now  universally  supposed  to  be  the  im- 
mediate seat.  But  Messrs.  Mariotte  and  Mery 
contended,  that  the  choroides  is  the  seat  of 
this  sense ; and  the  ancients  supposed  the 
crystalline  to  be  so.  Besides  the  optic,  the 
eye  receives  branches  from  the  third,  fourth, 
fifth,  and  sixth  pair  of  nerves. 

The  humours  of  the  eye,  together  with  the 
cornea,  are  calculated  to  refract  and  converge 
the  rays  of  light  in  such  a manner  as  to  form 
at  the  bottom  of  the  eye  a distinct  image  of  the 
object  we  look  at;  and  the  point  where  these 
rays  meet  is  called  th & focus  of  the  eye.  On 
the  retina,  as  in  the  camera  obscura , the  ob- 
ject is  painted  in  an  inverted  position;  and  it 
is  only  by  habit  that  we  are  enabled  to  judge 
of  its  true  situation,  and  likewise  of  its  dis- 
tance and  magnitude.  To  a young  gentleman 
who  was  born  blind,  and  who  was  couched  by 
Mr.  Cheselden,  every  object  (as  he  expressed 
himself)  seemed  to  touch  his  eyes  as  what  he 


A14t  Of  the  Senses  and  their  Organs. 

felt  did  his  skin ; and  he  thought  no  objects  so 
agreeable  as  those  which  were  smooth  and 
regular,  although  for  some  time  he  could  form 
no  judgment  of  their  shape,  or  guess  what  it 
was  in  any  of  them  that  was  pleasing  to  him. 

In  order  to  paint  objects  distinctly  on  the 
retina,  the  cornea  is  required  to  have  such  a 
degree  of  convexity,  that  the  rays  of  light  may 
be  collected  at  a certain  point,  so  as  to  termi- 
nate exactly  on  the  retina. — If  the  cornea  is 
too  prominent,  the  rays,  by  diverging  too  soon, 
will  be  united  before  they  reach  the  retina, 
as  is  the  case  with  near-sighted  people  or 
myopes  ; and  on  the  contrary,  if  it  is  not  suf- 
ficiently convex,  the  rays  will  not  be  perfectly 
united  when  they  reach  the  back  part  of  the 
eye ; and  this  happens  to  long-sighted  people 
or  presbi , being  found  constantly  to  take  place 
as  we  approach  to  old  age,  when  the  eye  gra- 
dually flattens.*  These  defects  are  to  be  sup- 
plied by  means  of  glasses.  He  who  has  too 
prominent  an  eye,  will  find  his  vision  improv- 
ed by  means  of  a concave  glass ; and  upon 
the  same  principles,  a convex  glass  will  be 
found  useful  to  a person  whose  eye  is  natu- 
rally too  flat. 

* Upon  this  principle,  they  who  in  their  youth  are  near  sight- 
ed may  expect  to  see  better  as  they  advance  in  life,  as  their  eyes 
gradually  become  more  flat. 


\n  ATOMY  Plate  AW 


Of  the  Senses  and  their  Organs.  415 


EXPLANATION  OF  PLATE  XXX. 

Figure  1.  Shows  the  Lachrymal  Canals, 
after  the  Common  Teguments  and  Bones 
have  been  cut  away. 

a,  The  lachrymal  gland,  b,  The  two  punc- 
ta  lachrymalia,  from  which  the  two  lachry- 
mal canals  proceed  to  c,  The  lachrymal  sac. 
d,  The  large  lachrymal  duct,  e,  Its  opening 
into  the  nose,  f,  The  caruncula  lachrymalis. 
g,  The  eye-ball. 


Fig.  2.  An  interior  View  of  the  Coats  and 
Humours  of  the  Eye. 

a a a a,  The  tunica  sclerotica  cut  in  four 
angles,  and  turned  back,  b b b b,  The  tunica 
choroides  adhering  to  the  inside  of  the  sclero- 
tica, and  the  ciliary  vessels  are  seen  passing 
over — c c,  The  retina  which  covers  the  vitre- 
ous humour.  d d,  The  ciliary  processes, 
which  were  continued  from  the  choroid  coat, 
e e,  The  iris,  f,  The  pupil. 


Fig.  3.  Shows  the  Optic  Nerves,  and  Mus- 
cles of  the  Eye. 

a a,  The  two  optic  nerves  before  they  meet, 
b,  The  two  optic  nerves  conjoined,  c,  The 


4 16  Of  the  Senses  and  their  Organs . 

right  optic  nerve,  cl,  Musculus  attollens  pal- 
pebrse  superioris.  e,  Attollens  oculi.  f,  Ab- 
ductor. g g,  Obliquus  superior,  or  trochle. 
aris.  h,  Adductor,  i,  The  eye-ball. 

Fig.  4.  Shows  the  Eye-ball  with  its  Muscles. 

a,  The  optic  nerve,  b,  Musculus  trochle- 
aris.  c,  Part  of  the  os  frontis,  to  which  the 
trochlea  or  pully  is  fixed,  through  which, — d, 
The  tendons  of  the  trochlearis  passes,  e,  At- 
tollens oculi.  f,  Adductor  oculi.  g,  Abduc- 
tor oculi.  h,  Obliquus  inferior,  i,  Part  of  the 
superior  maxillary  bone  to  which  it  is  fixed,  k. 
The  eye-ball. 

Fig.  5.  Represents  the  Nerves  and  Muscles 
of  the  Right  Eye,  after  part  of  the  Bones  of 
the  orbit  have  been  cut  away. 

A,  The  eye -ball.  B,  The  lachrymal  gland. 
C,  Musculus  abductor  oculi.  D,  Attollens. 
E,  Levator  palpebrte  superioris.  F,  Depres- 
sor oculi.  G,  Adductor.  H,  Obliquus  superi- 
or, with  its  pully.  I,  Its  insertion  into  the 
sclerotic  coat.  K,  Part  of  the  obliquus  inferior. 
L,  The  anterior  part  of  the  os  frontis  cut.  M, 
The  crista  galli  of  the  ethmoid  bone.  N,  The 
posterior  part  of  the  sphenoid  bone.  O,  Trans- 
verse spinous  process  of  the  sphenoid  bone. 
P,  The  carotid  artery,  denuded  where  it  pass- 
es through  the  bones.  Q,  The  carotid  artery 
within  the  cranium.  R,  The  ocular  artery. 


Of  the  Senses  and  their  Organs.  417 

Nerves. — a a,  The  optic  nerve,  b,  The 
third  pair. — c,  Its  joining  with  a branch  of  the 
first  branch  of  the  fifth  pair,  to  form  1, — The 
lenticular  ganglion,  which  sends  off  the  ciliary 
nerves,  d.  e e,  T he  fourth  pair,  f,  The  trunk 
of  the  fifth  pair,  g,  The  first  branch  of  the 
fifth  pair,  named  ophthalmic. — h,  The  frontal 
branch  of  it.  i,  Its  ciliary  branches,  along 
with  which  the  nasal  twig  is  sent  to  the  nose, 
k,  Its  branch  to  the  lachrymal  gland.  1, 
The  lenticular  ganglion.  m,  The  second 
branch  of  the  fifth  pair,  named  superior  max- 
illary. n,  The  third  branch  of  the  fifth  pair, 
named  inferior  maxillary,  o,  The  sixth  pair 
of  nerves, — which  sends  off  p,  The  beginning 
of  the  great  sympathetic,  q,  The  remainder  of 
the  sixth  pair,  spent  on  c,  The  abductor  oculi. 

Fig.  6.  Represents  the  head  of  a youth,  where 
the  upper  part  of  the  cranium  is  sawed  off, — 
to  show  the  upper  part  of  the  brain,  covered 
by  the  pia  mater,  the  vessels  of  which  are 
minutely  filled  with  wax. 

A A,  The  cut  edges  of  the  upper  part  of 
the  cranium.  B,  The  two  tables  and  interme- 
diate diploe.  B B,  1 he  two  hemispheres  of 
the  cerebrum.  C C,  The  incisure  made  by 
the  falx.  D,  Part  of  the  tentorium  cerebello 
super  expansum.  E,  Part  of  the  falx,  which 
is  fixed  to  the  crista  galli. 

3 G 


418  Of  the  Senses  and  their  Organs. 

Fig.  7.  Represents  the  parts  of  the  External 
Ear,  with  the  Parotid  Gland  and  its  Duct. 

a a,  The  helix,  b,  The  antihelix,  c,  The 
antitragus.  d,  The  tragus.  e,  The  lobe  of 
the  ear.  f,  The  cavitas  innominata.  g,  The 
scapha.  h,  The  concha.  i i,  The  parotid 
gland.  k,  A lymphatic  gland,  which  is  often 
found  before  the  tragus.  1,  The  duct  of  the 
parotid  gland,  m,  Its  opening  into  the  mouth. 

Fig.  8.  A view  of  the  posterior  part  of  the 
external  ear,  meatus  auditorius,  tympanum, 
with  the  small  bones,  and  Eustachian  tube 
of  the  right  side. 

a,  The  back  part  of  the  meatus,  with  the 
small  ceruminous  glands,  b,  The  incus.  c, 
Malleus,  d,  The  chorda  tympani.  e,  Mem- 
brana  tympani.  f,  The  Eustachian  tube,  g, 
Its  mouth  from  the  fauces. 

Fig.  9.  Represents  the  anterior  part  of  the 
right  external  ear,  the  cavity  of  the  tympa- 
num— its  small  bones,  cochlea,  and  semicir- 
cular canals. 

a,  The  malleus,  b,  Incus  with  its  long  leg, 
resting  upon  the  stapes,  c,  Membrana  tym- 
pani. d,  e,  The  Eustachian  tube,  covered  by 
part  of — f f,  The  musculus  circumfiexus  palati. 
1,  2,  3,  The  three  semicircular  canals.  4, 
The  vestible.  5,  The  cochlea.  6,  The  por- 
tio  mollis  of  the  seventh  pair  of  nerves. 


Of  the  Senses  and  their  Organs.  419 

Fig.  10.  Shows  the  muscles  which  compose 
the  fleshy  substance  of  the  Tongue. 

a a,  The  tip  of  the  tongue,  with  some  of  the 
papillae  minimae.  b,  The  root  of  the  tongue, 
c,  Part  of  the  membrane  of  the  tongue,  which 
covered  the  epiglottis.  d d,  Part  of  the  mus- 
culus  hyo-glossus.  e,  The  lingualis.  f,  Ge- 
nio-glossus.  g g,  Part  of  the  stylo-glossus. 


THE  END. 





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